DCweather

Risk of Snow Showers tomorrow, cold for Friday

2008-01-23T17:19:00.000-05:00

Current Weather:
Temperatures currently in the lower 40s should drop into the mid 20s overnight under mainly clear skies and light winds in and around the Beltway. Farther to the north and west, temperatures are presently in the mid to upper 30s, and should fall into the upper teens overnight.

Forecasts For the Next Few Days:
Thursday:
By 8 or 9 AM tomorrow, clouds should begin streaming in from the west, as energy associated with a tiny pocket of mid and upper level energy slides east from the Midwest. High temperatures tomorrow will hover in the lower to mid 30s in and around DC, which will support a few snow showers, which may develop during the late morning and into the late afternoon hours. Some minor snow accumulation is possible on grassy and elevated surfaces, but most roadways should remain snow-free due to above-freezing road temperatures.

Probability of Snow: 40%

Image at right: NAM forecast precipitation for Thursday afternoon showing the possibility of some light snow showers around the metro region. Image courtesy of the Penn State E-Wall

Friday:
Cold, Canadian air is expected to pour into the region overnight Thursday as a cold front sweeps through the Mid Atlantic. Temperatures early Friday morning will range from 15 around Hagerstown and surrounding areas, to near 20 near Washington, D.C.

Clouds should scour out by mid morning, leaving us with mainly sunny to skies. High temperatures will be in the upper 20s and lower 30s.

Saturday:
Clouds will increase late Friday night and into Saturday morning as a very weak upper level disturbance rotates through the region. At this point, there does not appear to be enough lift to get any precipitation over the mountains. Temperatures will hover around 40.

Paying Attention to What the Forecaster Actually Says:
With the recent forecasts of snow in the metro region, it has gotten to me when people ask me, "hey, the weather channel said there was supposed to be snow last night. How come there was none/How come it didn't stick?"

It seems incredible to me that, with all the precision and time forecasters put into their work, the vast majority of the public really doesn't pay attention to some of the crucial details. Here's a portion of the text forecast for Montgomery county for Thursday from the National Weather Service:

.THURSDAY...MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS. HIGHS IN THE UPPER 30S. NORTHWEST WINDS 10 TO 15 MPH. GUSTS TO 30 MPH IN THE AFTERNOON. CHANCE OF SNOW 40 PERCENT.

Seems simple enough, right? Now, take a quick look at the image to the right. It's The Weather Channel's forecast for Thursday. If it DIDN'T snow at all tomorrow, I would bet that most people would say, "the meteorologists got it wrong again. Where was the snow??"

Very few public viewers actually take the time to read the forecast text. Notice that little percentage at the bottom? In the NWS text forecast, this percentage is 40%, and in The Weather Channel's it's 30%. These are known as Probabilities of Precipitation.

Most people think of POP as the percentage of getting precipitation on that day. That, unfortunately, is only one part of the formula. POP is based on two things:

1) The probability that any precipitation will fall in the time period and
2) The predicted areal coverage if precipitation actually develops

So take this hypothetical situation (it would more than likely never happen, but what the heck):
Washington, D.C. records a POP of 20% for 100 consecutive days. If this POP were accurate over the long term, then Washington should have experienced some type of precipitation for 20 of those 100 days (not a great number, right?) The likelihood of precipitation being recorded when the POP is 20% is extremely low.

So, the next time you read or hear a forecast, it would be wise to also look or listen for the Probability of Precipitation. Weather isn't exactly and exact science.

Nuisance Snow storm tomorrow

2008-01-16T17:34:00.000-05:00

Current Conditions:
Temperatures are currently hovering in the mid to upper 30s across most of the region, with Reagan National as the warm spot at 41 degrees last hour. Temperatures are expected to fall into the low to mid 20s overnight as clouds thicken from the south and west, as a large developing surface low moves northeastward.

The snowfall forecast for tomorrow is a tricky one, since surface temperatures, once again, will be very marginal for accumulations.

Winter Storm Breakdown:
Snow should begin to fall by 12PM or so in the District, earlier to the southwest, and later to the north and east. The surface temperature profile will be critical to this forecast. At this point, our best estimate is that the snow will change to sleet and then rain by 4-6PM as warm air filters in from the east.

By the time the precipitation change-over occurs, however, there is the potential for a Trace to 2 inches of snow in and around the District, and 1-3 inches out to the north and west of town, where temperatures will likely remain colder.

If temperatures fall just a few degrees below forecast levels, a significant change to snowfall totals would be needed. At this point, however, I am not convinced areas in and around the District stay below 32 for very long after 4 or 5PM.

Snowfall Forecast:
I think most locations, even out towards Martinsburg, WV and Harisonburg, VA will change over to rain, it will just take longer, thus the higher snowfall totals out that way. There will likely also be a period of freezing rain in the lower portions of the Shenandoah and out towards Garret County, MD. I anticipate a light glaze of ice around the aforementioned areas.

Colder weather in the future

2008-01-14T14:55:00.000-05:00

Current Conditions:
Temperatures around the region are currently hovering near 40 degrees, but a weak surface trough has just cleared the area, which should usher in slightly colder temperatures for tonight.

Washington, D.C. reported 0.03" of rain with the storm system last night, and BWI only picked up about 0.07" from a thin line of showers.

Many areas to the north, were anticipating snowfall totals at or above 12", but most locations only received (generally) between 3 and 6 inches. Numerical computer models failed to accurately predict the dynamics of this coastal low, which lead to significant forecast busts across the Northeast.

Tonight and Tomorrow:
The sun is breaking out in many locations as a large winter storm, currently hammering upstate Maine with heavy snow, slowly pulls away to the northeast (see image above).

Skies will continue to clear, gradually overnight. Temperatures will fall into the mid to upper 20s around town, and near 20 farther to the north and west.

Expect partly cloudy conditions tomorrow, with temperatures rising in the lower 40s by mid afternoon. Breezy northwest winds will make it feel like it's in the upper 30s, however.

Entering a Cold and Stormy Pattern--Snow is again a Possibility:
STORM 1:
A few models have been hinting at the possibility of yet another coastal storm developing Thursday night and Friday morning. While precipitation may start off as either a mix of rain and snow, or pure snow Thursday night, thermal profiles would seem to favor everything changing over to rain by Friday morning.

(Image at right: Surface precipitation and temperatures about 10,000 feet up. Notice how DC is above freezing at this level (+2C or so) which, with surface temperatures above freezing, would translate into rain for the Mid Atlantic).

So at this point, here's the forecast: Brief period of rain/snow Thursday night, quickly changing to rain by midnight. Things could change, but significant changes look unlikely at this point.

STORM 2:
On the heels of the aforementioned storm is yet another disturbance which has the potential to drop snow on the region. While not a classic set-up, current forecasts offer us a slightly higher probability of snowfall Saturday through Sunday evening.

After these storms move by, a massive outbreak of Canadian Cold air is forecast to overrun much of the United States in below-average temperatures from around Sunday, January 20th, through the end of the month.

Coastal Storm Possible on Monday?

2008-01-10T16:06:00.000-05:00

Where's the Storm Now?
The feature we expect to develop into a coastal storm is currently a highly disorganized area of cloudiness associated with impulses of upper air energy over the northeastern Atlantic Ocean (see image at right). These little "packets" of energy are expected to slide southeastward, following the jet stream, and then combine--or phase--to produce a surface low pressure system in the Northwestern Gulf of Mexico sometime Saturday night.

This much of the forecast is pretty much a 100% certainty at this point.

What happens next, however, is difficult to assess with great confidence right now, as there are too many different things that have to click just right to produce a significant winter storm for our region.

What the models are saying:
Global Forecast System (GFS): We use this model the most to diagnose weather patterns over the United States. It has a decent track record (over the past several years), but has not been performing too well this winter. The past two runs of this model reveal a pretty much ideal situation for a significant snowstorm in the major I-95 Cities, from Washington, D.C. to Boston, MA.

North American Mesoscale (NAM): One of the worst performing numerical weather models beyond 48 hours this year. Nevertheless, it has begun to move towards a solutions that mirrors that of the aforementioned GFS. Surface temperatures will likely be an issue (mid to upper 30s).

Canadian Model: I feel this model has performed very well so far this winter. While it develops a significant surface low, it's roughly 200-300 miles off the coast--too far away to dump any appreciable precipitation on the region. (See image at right: bottom right panel is surface precipitation valid late Sunday night).

The European Model: By far, one of the best out there for medium-range forecasting, but is rather poor inside of 84 hours. Previous runs have developed a very nice storm for us, but this morning's run develops the low even farther east than the Canadian.

Current Thinking:
We are confident there will be a storm of some kind Sunday night into Monday. Whether it remains cold enough for snow, however, is still up in the air. Our airmass is not particularly cold, and any coastal low that develops will have to move within a swath 100 to 150 miles offshore to give us any hope of receiving snowfall.

At this point, temperatures look to remain in the upper 30s to near 40 for most of us, which would lead me towards a rain, or rain/snow mix solution for Sunday night/Monday. If the GFS does verify, however, much of the precip would be snow. Stay tuned.

Funky DC weather

2007-12-12T17:09:00.001-05:00

Most of the precipitation with this winter storm (at least before Sunday morning) will fall in the form of sleet or freezing rain. Areas in extreme Northwestern Maryland have the best chances of seeing accumulating snow, but even there, warm surface temperatures may turn things over to rain briefly during the afternoon.

As for the District and Baltimore, this now looks like a primarily rain event. We may see a few flakes or sleet pellets before the storm ends tomorrow afternoon as cold air filters down from the northwest.

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A Winter Weather Advisory is in effect from 3AM to Noon for areas north and west of the District including Montgomery, Loudon and Howard Counties. The National Weather Service anticipates icy conditions tomorrow morning.

Icy situation tomorrow morning:
Models over the past few days have trended cooler with a developing low pressure system in the southern United States. Temperatures are expected to cool into the low to mid 30s north and west of the District. As the upper levels warm above freezing, sleet and freezing rain are slated to develop around the aforementioned areas sometime tomorrow morning.

I don't really see this storm being much of a wintry event for the immediate metro regions, but northern sections of Montgomery and Loudon counties and points north and west could be in for a slippery ride tomorrow. Anywhere from a trace to one tenth of an inch of ice accumulation is expected before everything turns over the rain by midday.

After this storm exits the region tomorrow evening, our full attention turns to a potential large coastal storm.

To Snow or not to Snow:
Numerical model runs on Tuesday afternoon turned most Washington snow-lovers euphoric. The normally trustworthy GFS pumped out an eye-popping 18-24"+ of snow for most I-95 cities on Saturday through Sunday. Recent runs, however, have brought the storm farther inland, and instead of a monster pure snow event, forecasts snow changing over to plain rain.

But, there are some very promising signs that things are about to change. The newest computer model runs hint at the possibility that the low scoots a bit farther east, bringing a prolonged period of snow back into the equation. It's still too early, and I'm too uncertain, to make any calls at this point, but the potential for a large winter storm is still a very real possibility.

Soggy, wet pattern setting up this week

2007-12-09T18:41:00.000-05:00

Current Weather:
Presently, a developing area of low pressure around the Ohio River valley is pushing rain showers into northern Maryland from west to east.

The current thinking is that rain showers will stay generally north of Washington until tomorrow around noon as bands of light precipitation move southward as a small cell of high pressure pushes in from the northwest. Even with the high pressure in place for Tuesday, skies are expected to remain generally cloudy with high temperatures climbing into the upper 50s to near 60.

While our temperatures remain warm enough for a pure rain event, folks up in New York and northern Pennsylvania are in for a significant icing event. Freezing rain is expected to coat the region in over a quarter inch of ice.

Forecast through the rest of the week:
Another developing low during the middle of the week is expected to bring the area yet another shot at some light rainfall. Our chances for rain will slowly increase through the day on Wednesday as a warm front lifts north of the region before the low moves east by Thursday evening.

Even with all this rain in the forecast (looking at the National Weather Service forecasts, you'll see rain symbols every single period up until Thursday), just know it will not be raining every single minute for the next 4 days. We will have sporadic, elevated chances of rainfall through the week, with the best chances coming during the day tomorrow and Wednesday night into Thursday.

Rainfall accumulations are quite high through the week given all of these stubborn low pressure systems. The graphic to the right show total precipitation accumulations through Friday night as forecast by the GFS (Global Forecast System) model. Granted, I think the totals are too high for most locations, but it just gives you an idea of how much moisture there is in the atmosphere this week.

Image above: GFS Total precipitation accumulations through 00Z Saturday. Courtesy of Accuweather.

I thought Hurricane Season was over?
Hurricane season officially ended on November 30, but the National Hurricane Center is monitoring a disturbance in the Caribbean that may develop into yet another tropical system:

WATER TEMPERATURES ARE STILL WARM ENOUGH IN THIS AREA TO
SUPPORT TROPICAL CYCLONE FORMATION...AND UPPER-LEVEL WINDS ARE NOT ESPECIALLY PROHIBITIVE FOR DEVELOPMENT. THIS SYSTEM HAS THE POTENTIAL TO BECOME A TROPICAL OR SUBTROPICAL STORM DURING THE NEXT 24 HOURS

Hurricane Season hasn't given up yet.

Midweek Clipper and DC area's first snowfall

2007-12-03T16:52:00.000-05:00

Snowfall Update:
This clipper has turned out to be a fairly significant snow producer. Most locations north and west of the District will end up receiving 2-5 inches with locally higher amounts west of the Blue Ridge.

It appears as if at least light snow will continue around the metro region for another hour or two before everything shuts off from northwest to southeast.

--Previous Post--

The low that passed a strong cold front through the area yesterday is currently deepening off the coast of Maine, where up to two feet of snow is expected by tomorrow morning. The tight pressure gradient behind this storm is driving cold northwesterly winds down from Canada. Cold air continues to filter into the region, and temperatures tomorrow will struggle to get into the low 40s. Winds will also turn gusty in the afternoon with 30-40 mph gusts likely in most locations.

This new pool of cold air will set the stage for the Washington metro areas first snowfall of the winter season:

By late tomorrow night, a piece of energy from a strong Pacific Northwest storm system will have been ejected southeastward into the Midwest (image at right). Clear, to partly cloudy skies Tuesday night will allow much of the daytime heating to radiate out, allowing temperatures to drop into the mid to upper 20s.

At this point, timing the onset of precipitation is very difficult due to a dry surface (or boundary layer) that will be in place early Wednesday morning. Any precipitation that develops over the area will evaporate before reaching the ground. The current thinking is light snow will start falling between 5 and 7AM on Wednesday.

As the snow falls into the dry boundary layer, surface temperatures will likely fall a few more degrees towards the wet bulb, which is simply the temperature to which the atmosphere will cool at 100% saturation (i.e. when the snow falls).

Snow should become a little heavier during the early afternoon hours as the clipper begins to slide south of us. In the image above, snow growth levels have fallen to near 12,000 feet and have begun to intersect areas of moderate to high omega (lifting) values. This often indicates a period of heavier snowfall, depending on the magnitude of the forcing. In this case, forcing is decent, but not great, which would support a period of moderate snowfall rates around 12 to 5 or 6PM.

Afternoon temperatures on Wednesday may pose a problem for snowfall accumulations, as they may rise slightly above freezing. My best guess on snowfall totals at this point is between 1-3 inches on elevated or grassy surfaces, and a Trace-2 inches on untreated roadways and sidewalks.

This will only be a "nuisance" snow event, but since it's the first of the season, and snow will likely begin before rush hour, it may cause some problems for Wednesday morning commuters.

DCweather's Winter Outlook

2007-11-28T18:23:00.000-05:00

Precipitation Forecast:
Over the years, the ENSO (El Niño-Southern Oscillation) Index has been used, to great effect, to predict long term inter-seasonal variability in temperature anomalies across the United States. Generally, La Niña occurs when Sea Surface Temperature Anomalies from an area bounded from 5°N-5°S 120°W-170°W (also known as Niño 3.4) drop to less than 0.5 degrees Celsius.

Boxed areas represent the so-called Niño regions. Niño 3.4 is generally used in most long-term forecasts. Image courtesy of the Climate Prediction Center

At the end of the August-September-October time period, Niño 3.4 was at -0.8 and falling, meaning average SST anomalies for that region were 0.8 degrees Celsius below normal. Model forecast for the ENSO index indicate that SSTs should continue to fall through the remainder of the year and into next January. The NCEP CFS model, in particular, drops the ENSO index down below -2, which would approach some of the lowest monthly values every recorded.

More likely, however, is the threat of a moderate to strong La Niña through next January which would indicate drier than normal conditions across the Southeast and Mid Atlantic States, and generally warmer than average temperatures.

La Niña generally predicts precipitation anomalies a little better than temperature anomalies, at least in this part of the United States, so I am using the ENSO index more for this aspect of the winter forecast.

In short, I anticipate a drier-than-normal period from December through next January for the entire Southeast and Mid Atlantic. (This could be a bad thing for you snow-lovers, but keep reading).

Temperature Forecast:
Temperatures are normally a little harder to predict this far in advance. Unlike the teleconnections for precipitation, the comparisons aren't as black and white. Temperatures can be affected by the position of the jet stream, North Atlantic Oscillation, Pacific/North American Pattern, the Arctic Oscillation, Southern Oscillation Index, and a list that goes on too long to complete.

As a rule, though, the North Atlantic Oscillation (NAO) and Pacific/North American Pattern (PNA) are the most reliable predictors of temperature anomalies.

The NAO index, which measures pressure differentials between areas around Greenland, is currently at 0.45 and falling slowly. Likewise the PNA was 0.55 and falling rapidly. The years that best represented our current set-up are: 1963, 1969, 1995, and 2005. These years produced below-normal temperature anomalies across the Eastern third of the country, as seen at right.

Based on this information, and combining it with the fact that the ENSO should be negative for much of the winter, I think temperatures will be average to slightly below average through January.

Snowfall:
With La Niña in place, we will likely not be seeing an above average year for snowfall. However, I think we may be able to squeeze out a slightly below average year for most of the area (that works out to be around 10-14 inches at Reagan National, and 13-16 inches up north towards Baltimore. There will likely be more storms that drop a mixture of snow, rain, and freezing rain over the Mid Atlantic due to the milder air.

Running Clipper Happy

2007-11-08T16:48:00.000-05:00

If there is one thing I have learned over the years, it is that computer models do not ever do a good job with clipper systems. In fact, you'll see in my previous entry which came last weekend I talked about how a clipper could give us some snowflakes Friday night- Saturday if everything went as the GFS was showing on that day. But between Sunday and Wednesday, the clipper all but disappeared from the computer models.... until today.

It now looks likely that a clipper will pass through the area just to our south and west. As it does so, it will spread precip into the entire area. The question is, what form will it come in? Unfortunatly, I don't really have an answer. Looking at the conditional probabilities on the NAM and GFS, it could go either way. If I were to had to put something on it, I don't think anyone south and east of DC will see anything in the way of snow, and snow in the district may be a stretch. I do think it is fairly possible that the immediate suburbs of Montgomery, Fairfax, Frederick (etc) could see snow.

It will all come down to a couple of degrees Friday night, so if you are rooting for the first flakes of the year, stay close to a thermometer!

(I'd show you a picture here but there have been some technical difficulties...)

Welcome to winter next week!

2007-11-03T12:40:00.000-05:00

A strong cold front will cross the area Monday night and send us into a very winter-like pattern for the remainder of next week. Temps will fall during the day Tuesday, with highs in the low 50s and gusty winds. On Wednesday and Thursday, highs will struggle to get out of the 40s, with nighttime lows in the 20s to around 30 in the city. Things will get interesting on Friday:

The GFS and EURO models have been hinting that two clippers, particularly the latter, may give us our first snow of the year. The first clipper is the weaker of the two, and and would perhaps give us a few flurries/drizzle on Wednesday night-Thursday. The bigger storm would be Friday night-Saturday.

If this were January, I would say that this storm would have the potential for several inches of snow.... but its November. As such, it is possible that if everything were to go right that we get some snowflakes or a very chilly rain during the period in question. Lots can change between now and then, but the underlying theme here is that a winter-like pattern will take shape next week.

12z GFS showing moderate snow over the area on Friday.

Severe Storms Friday...An end to the drought pattern?

2007-10-17T16:50:00.000-05:00

Hello Everyone... just an update on the status of the blog first off. We haven't really done any updates in a week or so because, well, there hasn't really been much to talk about. This is a blog where we take a look into upcoming weather events in the area that might actually change your day-to-day activities...

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Friday's severe threat:

A very rigorous storm system has developed over the plains today spawning multiple tornadoes and a number of severe thunderstorms across the area ahead of the dry line in Oklahoma. This storm system will deepen as it moves east over the next couple of days, and does pose the risk for a severe thunderstorm outbreak on Friday.

NWS has gone with a 30% chance for Day 3, which is pretty high for storm outlooks beyond 48 hours.

Computer models are suggesting that EHI values (a measure that can indicate how probable a thunderstorm is of dropping a tornado) will be on the high side (2-3 across the area). The bigger risk, however, will be straight line winds; the cold front will be cruising across the area, and models are indicating that a number of long bow echos may evolve on Friday afternoon as the storm crosses the Apalachians. The one thing I see as a potential inhibbiting factor is the left-over cloud cover from tomorrows storms. We will talk about this more tomorrow.

Sheer is when wind directions at different levels of the atmosphere are moving in different directions. On Friday, winds will be coming out of the southeast at the surface, but out of the northwest aloft--- this will create spin in the atmosphere for supercells and long-lived bow echos

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A break from the Dry Pattern?

Yes we are a significant drought- "extreme" in some southwestern suburbs according to the NWS. The question is, are we going to break the dry pattern?

While I do see two good chances of significant rain over the week or so, I do not see a pattern change in near future. Hopefully, we will be able to get 1-3 inches of rain like the GFS indicates over the next week, because I still see strong Bermuda Highs sitting to our east 10+ days from now.

Storms lining up for Evening...

2007-09-27T15:56:00.000-05:00

A SEVERE THUNDERSTORM WATCH IS IN EFFECT UNTIL 10:00 PM EST FOR THE 1-81 CORRIDOR WESTWARD.

Discussion: A slow moving front will put an end to our unseasonable heat tonight, and as it does so, severe thunderstorms will be possible across the northern and western suburbs. The biggest risk for these storms is the heavy rainfall, which could exceed 1-3 inches/hour in heavier cells.

We need all the rain we can get, and its quite possible that the immediate metro area sees a solid half inch of rainfall tonight as the storms move weaken as they push into the area. I am confident that most locales will see some rain with this system, although the true soaking rain will stay north and west of the immediate DC area.

Projected times of the first drops:
Winchester: 5:30
Hagerstown: 6:00
Frederick: 6:30 (although a pop-up storm did drop some rain earlier today...)
Werenton: 7:30
Fairfax: 9:00
Rockville: 9:30
Washington D.C.: 10:00
Baltimore: 10:30
Anapolis: 11:00
Fredericksburg south: rain not likely.

A line of strong storms has the potential of dropping some significant rain over the area tonight.

Nice weather for Weekend...Watching Gulf of Mexico closely

2007-09-20T20:11:00.000-05:00

Nice weather is on tap for the weekend as a weak cold front approaches the area from the northwest. Winds wil shift to the southwest on Friday bringing in almost August-type heat and humidity. While we can't rule out a shower or thunderstorm on Saturday, skies will remain more or less clear for the weekend.

A weak cold front will fizzle out on Saturday as it approaches the area. Expect a Summer-like weekend with temps in the mid 80s both days.

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Watching Invest 93L:

The National Hurricane Center investigated invest 93L in the Gulf of Mexico near Florida and found a well-defined low-level center and a pressure of 1006mb (what you would expect in a tropical depression). The only issue is that the system doesn't have very many tropical features at the moment, with little convection near the low-level center. None the less, conditions are becoming favorable for 93L to become a sub-tropical or tropical storm in the next day or two as it drifts westward. People in the southern Gulf should pay attention to this system--- computer models seem to agree that the most likely place for the system to make landfall would be western Louisiana. From there, it is possible that we get some rain just as we did when Gabby came ashore in Texas last week.

Storms lining up for this evening....

2007-09-10T14:58:00.000-05:00

Heavy rainfall associated with slow moving thunderstorms will be possible over the next several hours as a wave of low pressure moves up a nearly stationary front and spreads moisture over the extremely humid air mass in place (Gabriel left behind very high dew points when it departed).

Although a widespread severe weather event is not anticipated, a couple of damaging wind reports are possible. The heavy rainfall, in some of the heavier cells though will be the main threat. Hopefully we can get some rain from this system...

Radar does not look too impressive right now, but by this evening, heavy thunderstorms will blanket the area...

Gabriel a close call...

2007-09-08T22:30:00.000-05:00

It took a little longer than expected, but the area of disturbed weather off the North Carolina Coast finally became tropical in nature this afternoon (at first, the NHS listed it as a subtropical storm....don't ask me what made it "tropical" by 5pm but "sub-tropical" at 2pm).

At this point, Gabriel is a weak tropical storm with winds sustained at 40mph (although I do think that may be underdone a bit). While the track of Gabby (below) indicates that nobody west of the Eastern Shore will be impacted by the storm, in recent hours, the tropical storm has wobbled a bit west which may in turn take the track a bit further west.

This westward trend must be monitored, and I do still think that there is an outside chance that Gabby reached hurricane status before making landfall in Eastern Carolina. Unless something drastic happens however, it doesn't look like Gabby will be one for the memories.

Gabriel looking better tonight...

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In other weather news, a slowly dropping front (the same front that is going to keep Gabriel away) will give us a chance for some storms Monday. Some of these storms on Monday may reach severe limits. After there, it looks like a clear and calm weather pattern will settle in, giving us seasonable weather for the remainder of the workweek.

Soon-to-be Gabriel is something to watch...

2007-09-05T16:36:00.000-05:00

At 3:30pm Wednesday, new recon reports showed that the area of circulation southwest of Bermuda is very close to tropical depression status. Chances are high that by Thursday we will have tropical storm Gabriel, and computer models are indicating that there is a chance that Gabriel will strenghten and move west towards the North Carolina Coast, potentially impacting the DC area by the end of this weekend with heavy rain and strong winds.

Stay tuned...

Perfect stretch of weather to continue... Felix, 98L developing...

2007-09-01T14:41:00.000-05:00

Sunday Night Update: Hurricane Felix strengthened rapidly today, reaching category 5 status this evening. Just to get a sense of the strength of this storm, when NOAA recon planes flew into the storm earlier today, they found lightning in all quadrents (usually something we only see in hurricanes that are truly exploding in intensity) and graupel (small frozen water droplets/hail that can were obviously large enough to damage the plane), and ultimately had to abort the mission. The plane also recorded a 1mb drop in pressure per mile when flying into the storm. That will make your ears pop like CRAZY!!! Felix should level out in terms of winds Monday, and continue fluxuating in intensity between strong CAT 4 or CAT 5 until its landfall.

There is little change in the forcasted path--- Felix should continue west-northwestward towards Northern Honduras and Belize. There is still a slight chance that Felix will move far enough north to make a US landfall in Texas after its initial landfall somewhere in Belize or the Yucatan.

CAT 5 Felix Sunday night

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On the home front, a strong ridge of high pressure has moved into the area, and there is no indication that anything other than sunny skies and warm temperatures will persist well into the future. Temperatures will start to get up there to around 90 by Labor Day, and stay in the upper 80s through the week with no rain in the forecast.

A perfect weekend followed by a perfect week of weather

On to the tropics, where things are starting to heat up again:

Felix: Hurricane Felix (winds sustained at 70mph on Saturday) will continue to move west-northwestward towards the southern Carribean. Most of the models keep the storm well south of the Gulf Coast and take the storm into the Yucatan Penninsula, however some models have begun to shift northward. Trends will need to monitored.

98L: This system has strengthened significantly today, and should reach tropical depression status by tonight or tomorrow. It is far to early to tell, but 98L has a chance to be threat to the east coast by next week.

Rain on the Way for DC, Dean to ravage Jamaica

2007-08-18T14:54:00.000-05:00

Weather over the next several days:
Clear skies dominate over the Mid Atlantic as a ridge of high pressure builds into the region from the northwest. Clouds will, however, begin to increase out of the southwest shortly as a developing storm system slides eastward from the Central Midwest.

Temperatures: The increased cloud cover on Sunday should hold high temperatures in the low to mid 80s, which is at or slightly below average for this time of year.

Precipitation: The chance for a few showers/thundershowers will slowly increase after 7 or 8 PM Sunday evening. It appears, however, that the majority of the rainfall from this system will stay north of the Mason-Dixon line until Monday night. A few numerical weather models depict the possibility of severe thunderstorms moving into the region Tuesday morning and early afternoon. Needless to say, from Monday through Wednesday, scattered to numerous showers and thunderstorms will plague the region, but should significantly cut into the areas rainfall deficit.

Gulf Coast be Warned! Catastrophic hurricane is on the way:
Scalding hot sea surface temperatures, low wind shear, and slow steering currents are all coming together, (or rather, have come together) to form the most intense tropical cyclone this year. Hurricane Dean is currently an upper Category 4 Hurricane with maximum sustained winds of 150 mph near his eye.

This tropical monster has already ravaged portions of the Lesser Antilles, and is headed towards the island of Jamaica as a potential Category 5, which would completely devastate the mountainous region. According to Associated Press, NASA has shortened its spacewalk by one day, and will bring the astronauts back on Tuesday to avoid any potentially dangerous ramifications.

Folks anywhere from New Orleans to Tampico in east central Mexico need to prepare for this dangerous storm. While computer models seem to have converged on a general solution for landfall (around Brownsville, Texas plus or minus 150 miles) climatology points towards Dean turning northeast once he enters the Gulf of Mexico--towards Louisiana and New Orleans (CLP-5 model is the National Hurricane Center's climatology model).

This is an extremely powerful and dangerous tropical system. Jamaica will likely suffer from a direct hit from Hurricane Dean's extreme winds, surge, and rainfall. I expect catastrophic damage on the island in 36 to 48 hours.

Time to focus on Dean

2007-08-16T21:59:00.000-05:00

Hurricane Dean continued to strengthen Thursday and it appears now that the computer models are beginning to hone in on the future track of the powerful storm.

Dean should cross the Windward Islands and Lesser Antilles Friday as a stong Category 2 storm, with winds between 100-110 mph. Some of the resort islands like Martinique may suffer substantial damage as the hurricane whips across the island chain.

After the islands, Dean should continue on a west-west/northwest track to just south of Jamaica Sunday with sustained winds of 120 mph or more. Next in line will be the Yucatan peninsula on Tuesday, with the storm possibly making landfall as a category 4 storm near Cozumel, Mexico.

After a short ride over the Yucatan, Dean should re-emerge in the Gulf of Mexico and continue re-organize itself before making a final landfall somewhere in the Gulf Coast, most likely Southern Texas.

Personally, I am not convinced that the computer models are doing to well dealing with Dean's rapid speed (on Thursday night it was traveling west at 25 mph), and the progression of the upper-level ridge in the northern Atlantic. As such, I think that Dean may head a little further north than indicated, and anyone west of the Alabama coast are game. None the less, it appears likely that a strong hurricane will potentially impact the Gulf Coast next Thursday or so.

Model spread for Dean

Severe weather outbreak Thursday... still watching tropics

2007-08-15T22:49:00.000-05:00

Severe Storms

A strong front will pass through the area late tonight and spark off some major thunderstorms. EHI values (a measure of the tornadic potential across the area) are expected to be tremendous this afternoon. I would expect a number of lines of thunderstorms with damaging winds, and a couple of isolated tornados this afternoon/evening. The deciding factor in whether or not we will see a major outbreak depends on how much sunlight we see during the day. Sunshine, of course leads to destabilization and enables thunderstorms to reach severe limits. Make sure to check watches/warnings as the day progresses.

Notice the very high EHI values on the top-right map. Isolated tornados are possible this afternoon/evening.

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Tropics:

Erin: Tropical storm Erin will make landfall in southern Texas today with winds of 40-50 mph. The major damage out of Texas will be flooding however.

Dean: Tropical Storm Dean is very close to reaching hurricane status. I would expect the storm to reach hurricane status later today. Recent computer guidence suggests that the storm will travel into the Gulf of Mexico. More to come...

Dean, Flossie, TD 5; Its going to be a long week....

2007-08-14T21:11:00.001-05:00

As announced several days ago here on DCweather, all of the computer models were indicating that the tropics were going to explode this week. They did not lie. We currently have 3 tropical systems, 2 in the atlantic, and one in particular to watch.

Flossie: Hurricane Flossie weakened Sunday as it moved over much cooler waters near Hawaii. None the less, Flossie is still a strong category 2 hurricane, and will give Hawaii a glancing blow of tropical storm force winds and several inches of rain Wednesday. I do think that the islands should get by without too much in the way of damage.Surfs up: Flossie will cause minimal damage as it travels just south of the Hawaiian Islands Wednesday. Meanwhile, surfers across the state are getting ready for some of the best waves of the year!

TD 5: At 11:00pm Tuesday night, the NHC announced that the tropical wave in the Gulf of Mexico had gotten itself together well enough to be considered a tropical depression. While this is not good news for southern Texas, if I could be selfish for a minute, it is great news for us. Recent computer runs are indicating that most of the moisture from TD 5 will get absorbed into a front that will give us a chance for substantial rain next week! Unfortunatly, TD 5 may drop 10+ inches of rain on southern Texas; an area that does not need another drop. Additionally, I believe that TD 5 will become Tropical Storm Erica before it makes landfall, and may cause some wind damage on the south Texas coast. Anybody from Galvalston to Corpus Christy should be on alert for updates.

TD 5 visible at the bottom of the image. Soon-to-be Erin will make a Texas landfall Thursday

Dean: Tropical Storm Dean had a rough Tuesday. Stronger than expected sheer infultrated the storm on the northeast end and made it dificult for development. None the less, the system is heading into a more favorable environment for development, and should reach hurricane status by Friday. Computer models shifted a bit further south today with regard to the track of Dean, but a NC landfall is not out of the question. If I were forced to make a bet, I would say that Florida would be the target of this storm, but again, the only thing we do know is that the storm will not be a 'fish-spinner' (a storm that hooks out to sea before reaching land) due to a ridge in the northern Atlantic.

Despite looking ragged on satellite, the center of Dean remained defined Tuesday, and further development is expected.

Invest 90 L strengthening in Atlantic...

2007-08-13T00:50:00.000-05:00

The tropical wave, Invest 90 L is likely going to upgraded to tropical depression status Monday. The system has strengthened significantly late Sunday, and now has an easily identified center of circulation. This system is still more than a week away from being something to seriously worry about, but none the less, still certainly worth watching.

Computer models suggest that Invest 90 L will strengthen as it heads due west over the next several days. After that--- who knows? The GFS has trended furthur south; to a landfall in southern Texas, but these models are wildly inaccurate for storms 10+ days away.

Rain anybody?

Some badly needed rain is in the forecast for later this week. Meanwhile, a couple of isolated storms are possible Monday, as a weak cold front approaches the area. Nothing severe is anticipated nor is any significant rainfall expected.

Later this week, a more vigorous cold front will give us our first taste of the fall. More importantly however, it will enable a number of systems to ride up along the boundary left by the front during the Friday-Sunday time frame and potentially give us some much needed rain.

Cooler temperatures and yes, maybe some rain (!), are in store for late this week.

(also note invest 90 L in the Carribean)

A few storms for Friday, tropics to explode next week...

2007-08-10T12:06:00.000-05:00

Friday will feature a couple of storms across the area. It does not look like any of these storms will reach severe limits because of a left-over storm complex from last night that is currently just off the Mid-atlantic coast. This storm complex will rob the area of the energy necessary for thunderstorm development.

Additionally, clouds have moved into the area in the last hour or so, and the spotty cloudcover will make it dificult for enough heating to go on for thunderstorms. That said, a couple of storms may reach severe limits this afternoon, so stay tuned.

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Now, to move important things--- the computer models (particularly the GFS) have been consistantly showing a tremendous CAT 4-5 Hurricane moving up the East Coast late next week. Now, an important question must be asked: hype, or time to worry?

Well obviously there is no definate answer, but at least last year, the GFS frequesntly showed hurricanes beyond 10 days into the future only to take them off in subsequent runs. What worries me is that this hurricane has been on the maps for all of the last 11 runs, spanning 3 days. Additionally, the UKMET and Euro both now show this 'super hurricane'.

We will need to watch computer model trends closely in the next several days, but the most important thing to note here is that multiple sources seem to be indicating that the tropics are finally going to get going next week. Remember, the NWS still thinks we will be well above average in hurricane #s this year despite the slowish start.

A scary sight: many computer models are indicating that a large hurricane will impact the United States around the 20th of the month.

Major severe weather outbreak this afternoon/evening...

2007-08-09T08:49:00.000-05:00

4:00 UPDATE: One down, one to go. The first line of storms weakened as they moved into the immediate metro area, however significant damage was felt in northern Maryland. Although the watch box expired recently, another one will be issued shortly. This next batch of storms is heading out of SW PA at the current time and should be in the immediate metro area by 7pm or so. Stay tuned.

11:30 UPDATE: SEVERE THUNDERSTORM WARNINGS ARE IN EFFECT FOR FREDERICK, WASHINGTON, AND CARROL COUNTIES IN MARYLAND. There will be significant wind damage associated with this line of storms as they move across Northern Maryland in the next hour.

10:20 UPDATE: As soon as I finished writing the entry, a watch WAS issued for the area until 4pm. I will be doing updates as this dangerous line of storms moves into the area.

These are the projected times of arrival:

Hagerstown: 11:30am
Frederick: 12:00
Leesburg: 12:15pm
Rockville: 12:30pm
Silver Spring: 1:00pm
Bethesda: 1:00pm
Washington DC: 1:15pm

The NWS has extended the slight risk area for severe storms today to completely encompass the entire DC metro area. A moderate risk has also been discussed for parts of the area. Dangerous winds appear to be the biggest threat, however a tornado is not impossible.

Discussion: A dangerous line of severe storms is progressing through southwestern PA this morning. As this line continues to move east and southeast, it will head into increasingly unstable air (dewpoints are well into the 70s (!) and MLCAPE values on the order of 2500-3000 J/KG), this line will likely strengthen on its southern end as it moves into the region.

I am surprised a watch has not been issued with this line, as there have already been a number of damaging wind reports from interior PA this morning.

After this line goes through, there may be additional storms through the 10pm hour (the line should be out of the area by 5pm or so). Make sure to check radar befor heading out this afternoon... this line is cruising at a clip of 40-50 mph!

A dangerous line of storms will move into the area by the noon-2pm hour.

Additionally, the NWS issued a slight risk for severe storms tomorrow.... this will be a busy couple of days.

Storms stay west tonight... Major storms on tap for tomorrow, Friday

2007-08-08T14:27:00.000-05:00

SEVERE THUNDERSTORM WATCH IS IN EFFECT NORTH AND WEST OF DC FROM WASHINGTON COUNTY, MARYLAND TO HARDY COUNTY, WV WESTWARD UNTIL 10:00PM EST

Discussion: A line of storms that dropped golf-ball size hail in extreme southwestern PA is decending southeasterly at the current time. Unfortunatly, it does not look like the immediate metro area will see anything in the form of rain; the atmosphere is surprising stable this afternoon in spite of the relentless heat/humidity).

The best bet for rain tonight, as mentioned earlier is west towards I-81.

Chances for a shower/storm tonight:

Baltimore: 0%
Frederick: 10%
Washington DC: 20%
Winchester: 50%
Fairfax: 30%
Fredericksburg: 20%

Radar at 3:40 showing the line of storms in the panhandle of Maryland

After reaching 100 degrees in many areas today, relief is finally on the way in the form of severe thunderstorms associated with a boundary that will slip south of the area Friday. More on the severe storms for Thursday tomorrow...

Highest temperatures so far this year on the way, thunderstorms to follow

2007-08-06T10:44:00.001-05:00

Temperatures reached 90 degrees yesterday at the Nation's Capital, but with dewpoint temperatures in the low to mid 70s, the 90 degree heat became an oppressive 94 or 95 degree oven. Today, high temperatures will once again touch, if not eclipse, the 90 degree mark. High moisture levels will create heat index values in the mid to upper 90s. A few showers and strong to severe thunderstorms are possible later today as a weak upper level disturbance passes through the region.

The high temperatures and elevated dewpoints will contribute to large levels of instability this afternoon (see image at right). Convective Available Potential Energy (CAPE) is a measure of the relative amount of instability present in the atmosphere and is a good indication of the likelihood of severe weather. Values at or above 2000 Joules per kilogram are normally sufficient to sustain severe storms. The NAM model depicts CAPE values at or above 3000 J/kg later this afternoon. So, any storms that manage to develop today will have the potential to become severe. Working against the potential for severe storms are a lack of upper level wind shear, relatively little forcing to initiate convection, and dry mid-level air.

The Rest of the Week:
The main story for the rest of the week remains the heat. Temperatures are forecast to hit 97 or 98 degrees tomorrow and Wednesday. Heat Index values will soar into the triple digits due to high humidity and atmospheric moisture content.

A chance of thunderstorms will develop during the afternoon hours through the rest of the work-week, but the best chance of thunderstorms looks to come on Wednesday as a cold front sweeps through the area--probability of precip on Wednesday: 70%.

Severe Storms possible Sunday; Blistering Heat for the Workweek

2007-08-04T20:06:00.000-05:00

A couple of severe storms are possible Sunday as a subtle shortwave trough moves into the Central Appalacians. As it does so, a nearly stationary front will sit across the area and spark a round of severe storms. Air soundings for Sunday afternoon show a very steep low-level lapse rate and dew points well into the 60s.

What worries me is the perpendicular nature of the sheer in the atmosphere tomorrow--- that is, at the low-levels in the atmosphere, air will be flowing northeastward, while at the upper levels, air will be traveling southeastward. This perpendicualr nature of sheer allows thunderstorms to rotate, and produce hail and tornados. While a widespread severe weather event is not likely, if enough sun is able to destablize the atmosphere in the morning and early afternoon, a couple of storms may warrant warnings.

If storms do get going, 4-9pm would be time periodto watch... good news for folks heading out to watch the Nats try to win 6 straight at 1:35.

A very strong stationary front will sit over the region Sunday. Notice that lifted indexes are expected to be around -5 over the region tomorrow--- an important igrediant in severe weather.

Another important issue is the heat--- temperatures will climb well into the 90s, and may even touch 100 on Wednesday. Heat advisories will likely be issued.

Tropical Depression 3 Formed...

2007-07-31T00:49:00.000-05:00

UPDATE: Tropical depression 3 was upgraded to Tropical Storm status; Chantal is not a threat to the United States but may cause minor damage in eastern Newfoundland.

The NHC announced this evening that the disturbance just west of Burmuda had gained enough strength to warrant being named a tropical depression.

This storm has no chance of making US landfall, but may become a weak tropical storm before becoming extropical and absorbed into a strong cold front positioned well off the east coast.

Storm track for Tropical Depression 3, showing the storm potentially strengthening to tropical storm status before accelerating Northeastwardly toward Iceland.

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Meanwhile, nice weather, all be it hot, will dominate for the remainder of the workweek with a slight chance for a storm on Friday.

Nice, but hot weather to continue. Little rain in sight

2007-07-26T08:50:00.000-05:00

Rainfall Remains Sparse:
A persistent, cut-off upper level low pressure system continues to spin around over northern Ohio, and deliver showers to the Ohio River valley. The system will, unfortunately, fail to slide far enough to the east to deliver us any appreciable rainfall today or tomorrow. While there is a slight chance that some isolated areas receive rainfall from thunderstorms today, I would strongly bet against any precipitation around the region this afternoon.

A piece of upper level energy is expected to break off the main upper level low complex by Saturday morning, delivering a slightly better chance for some rainfall to the parched metro region. The North American Mesoscale Model (66 hour forecast depicted at right) seems to be over-doing rainfall totals around the Mid Atlantic, indicating one-half to three-quarters of an inch of accumulated precipitation by Monday morning. We will likely see some rainfall by the end of this weekend, but should total less than one half of an inch.

Has it really been an inactive hurricane season?:
Because of the massive increase in the number of tropical systems in the Atlantic Basin over the past few years, this year has, so far, seemed relatively tranquil. However, when compared to the 60-year average, this season is already above normal for the year.

According to the National Hurricane Center, on average, only 1.5 named systems (tropical storms), and fewer than one hurricane develops by the end of July. So far this year, two tropical storms have developed, one of which (Tropical Storm Barry) impacted south central Florida back in the beginning of June.

Currently in the Tropical Atlantic, while Sea Surface Temperatures remain anomalously warm in many areas, the upper level environment remains hostile to any potential development.
Upper level wind shear is high, which significantly inhibits tropical development. Furthermore, large quantities of Saharan dust (which are present in the Atlantic), blown across the Ocean at high altitude have been shown to inhibit the development of potential tropical cyclones.

Drought expanding with too much nice weather

2007-07-24T07:59:00.000-05:00

Today and Tomorrow:
Temperatures today should creep into the mid 80s around the District, to near 90 south of town. There is a slight risk of a few thunderstorms later this afternoon as daytime heating destabilizes the atmosphere.

Tomorrow, expect cloudier conditions than today as a weak mid and upper level impulse slides in from the west. There will be a slightly better chance of showers and thunderstorms than today.

Local Drought Expanding:
Since July 12, Reagan National Airport has reported only a Trace of rainfall, and our total monthly rainfall (1.33 inches) came on just four days during early June. Currently, rainfall deficits are running one to two inches below normal for the month from DC north and west. The exception is in Baltimore, where 1.8 inches of rain fell on July 10th during a severe thunderstorm.

Presently, nearly the entire Mid Atlantic is experiencing abnormally dry conditions, and the areas of moderate drought have expanded over the past few weeks.

While there is a chance of thunderstorms through this week, until we can get a large, persistent area of rainfall to sweep through the east coast, the developing drought conditions will get no better.

SEVERE THUNDERSTORM WATCH IN EFFECT UNTIL 10:00 PM EST

2007-07-19T13:15:00.000-05:00

2:20 UPDATE: SEVERE THUNDERSTORM WARNING FOR CULPEPER AND FAQUIER COUNTIES IN VIRGINIA. A couple of showers/storms will pass the immediate metro area in the next hour or so with most of the severe storms staying south.

The national Weather Service has issued a severe thunderstorm watch for the entire DC metro area until 10:00 PM tonight.

At first, the watch was a bit of a surprise to me due to the lack of daytime heating this morning and early afternooon, but a strong mid and low-level sheer has enabled a number of strong storms to develop across the area. Expect a couple of strong storms capable of damaging winds or small hail across the area.

An additional note about the watch is that it stays in effect until 10pm. The reason for this is simple--- the front is still in the Ohio Vallay! As the front continues to approach us, a number of lines that are currently developing over PA and WV may cross the area even as late as midnight. Remember yesterday, severe storms lasted until 4 AM across the Chicago-Cleveland area.

Radar image for 2:20 PM showing a very intense storm over Culpeper County and a couple of showers moving into the District.

One more Hot and Humid day before an End of the Week Reprive

2007-07-18T20:17:00.000-05:00

Tonight and Tomorrow:
It's currently 86 degrees at Washington Reagan National Airport and mostly cloudy to cloudy skies dominate the region. Expect temperatures to only fall another 10 or 12 degrees by early tomorrow morning.

We may start of with sunshine tomorrow, but clouds should gradually increase as a strong upper level impulse approaches the region from the west. Mid afternoon temperatures will likely rocket into the lower 90s before showers and thunderstorms begin breaking out across the region. The Storm Prediction Center currently has the Mid Atlantic outlined under a slight risk of severe thunderstorms for tomorrow afternoon and evening. I think a few strong to intense thunderstorms will develop around the metropolitan region, but most should remain under severe limits (hail greater than 3/4" and/or wind gusts 58 mph).

Image at right: Showers and thunderstorms developing throughout the Mid Atlantic and Northeast as temperatures soar into the upper 80s and lower 90s.

Image courtesy of the PSU Meteorology Website

Extended:
Showers and scattered thunderstorms will likely persist into the nighttime hours Thursday before clearing out of the region by Friday morning. Temperatures during the afternoon will return to near-normal levels (in the mid to upper 80s), and fall into the lower 80s for the weekend.

The British Open:
The 136th British Open Championship starts tomorrow, Thursday, at famed Carnoustie golf links in Carnoustie, Scotland. Showers are in the forecast for first round play, before clearing up for the second round on Friday.

Severe storms likely this afternoon...

2007-07-18T09:49:00.000-05:00

2:00 UPDATE: It doesn't look like there was enough destablization in the atmosphere this morning-early afternoon to allow a major severe weather outbreak. A couple of strong storms may emerge from the Mason-Dixon line and push south and east, but as a whole, we will have to wait until Thursday for a major outbreak of severe weather...

Radar image at 2:15 showing a couple of isolated storms around the area, but nothing severe. The best chance for seeing an isolated strong storm tonight will be east of the city.

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The National Weather Service has put the immediate metro ara under the slight risk area for severe storms for today and tomorrow.

This afternoon--- a weak shortwave associated with the residue from yesterday's storms over the upper Plains states (Iowa in particular) with pass through the area later this afternoon and kick off some thunderstorms in the process.

The one feature that the NWS indicated might reduce the risk of severe storms over the area is the lack of daytime heating. However, a look at the morning satelite (below) indicates that most of the area, with the exception I-495 remain cloudless at the current time.

Expect a number of storng storms capable of damaging winds or even an isolated tornado (EHI values and sheer are both respectable for the chance of a weak tornado). I would expect the NWS to issue a Severe Thunderstorm watch at around 2-3pm...

A look at the Satellite image at 10:45 AM today reveals that most of the area is undergoing modest daytime heating--- an important ingrediant for severe storms.

A break in the action today, more to come Wednesday-Friday...

2007-07-17T10:28:00.000-05:00

After a crazy afternoon yesterday, one in which nickel size hail and strong winds damaged a number of areas in northern Maryland and south-central Virginia, Tuesday will feature much calmer and more stable weather.

Wednesday-Friday, on the other hand will feature a return to the thunderstorms. Some of these storms particulary Thursday (it is still unclear whether or not the front will be able to clear the area by Friday afternoon) will have to be watched.

More to come tomorrow.

Can you see the front? Whenever you can go from 90% to 20% humidity in about 30 miles, you are going to see strong storms. (This is a map for 8pm Thursday).

SEVERE THUNDERSTORM WATCH IN EFFECT UNTIL 9:00 EST

2007-07-16T13:10:00.000-05:00

The National Weather Service has issued a severe thunderstorm watch for the entire DC metropolitan area until 9pm this evening.

Thunderstorms are increasing in coverage across the eastern slopes of the Appalachians, and

will move slowly into increasingly unstable air this afternoon.

What is most impressive however, is that the noon air sounding from the area recorded a lifted index at 500mb of around -4 degrees, which means that if a parcel of air is risen to 500mb (the middle layers of the atmosphere), it will be 4 degrees warmer than its environment and thus, continue to rise. As a result, cloud tops of over 55,000 feet will be possible in stronger storms.

It is likely that stronger complexes of storms will form bow echos this afternoon, so damaging winds appears to be the biggest risk with any storm that does form.

I think that the storms will be able to move into the immediate DC area from west to east between 5-7pm, although storms will be possible before then particularly south and west.

Radar image at 2:15 showing storms beginning to develop across the eastern slopes of the Appalachians, particularly south and west of DC.

Storms NW for Sunday, everywhere for workweek...

2007-07-15T00:58:00.000-05:00

Storms will be likely in the northern and western suburbs of DC Sunday evening, but it won't really be until Monday when most of the area sees widespread thunderstorms (some of which may be strong).

The OOZ NAM model (below) shows the linear nature of the storms Sunday evening over PA and WV drifting southeast, however, it doesn't look like these storms will have enough steam to reach the immediate metro area.

Areas north and west of line from Frederick to Winchester run the best risk for damaging winds with this line of storms, and it not impossible that the line sticks together long enough give even the immediate metro area some rain/thunder. If anything were to happen, it would not be until after 6pm.

Some thunderstorms may be strong to severe from Monday to Thursday as a stationary front keeps up humid and unstable, so additional updates will be provided.

Storms, but Nothing Out of the Ordinary...

2007-07-11T11:55:00.000-05:00

Those of you hoping for a major severe weather outbreak this afternoon are going to be dissapointed to hear that I don't believe there will be one in the immediate metro area.

A look at the satellite image tells the story (below).

Notice the cloud cover in advance of the cold front? This overcast will weaken our chances to get sufficent instability in the afternoon and evening.

The best chances for anything severe today in north and east of DC, although I do believe that most of the region will see something in the way of rain/thunder--- just nothing severe.

If any watches or warnings are issued, updates will be posted....

A Few Strong Storms Today, More Tomorrow...

2007-07-10T11:40:00.000-05:00

With air temperatures are in the upper 90s, and dew points are in the upper 60s, its easy to see why a number of storms have popped up over the region this afternoon. I doubt any of these storms will become severe, due to a lack of sheer in the atmosphere, but heavy rain and dangerous lightning are possible in some of the storms (I saw about 20 cloud-to-ground strokes of lightning with a storm that moved just east of my Silver Spring office at about 12:30pm today...). The best chance of for storms will be south and west of DC.

The National Weather Service has extended the slight risk area for severe weather to include the entire metropolitan DC area for tomorrow... damaging winds area the greatest risk.

Radar image at 12:50pm showing a number of pop-up storms across the area. Severe storms are not likely this afternoon, but tomorrow may be a different story.

An old-fashioned D.C. Heat Wave...

2007-07-06T14:38:00.001-05:00

A strong Bermuda high will keep us dry and warm through the rest of this week, and at least the first part of next week. Temperatures the next several days will climb well into the 90s, and may even approach 100 degrees by Monday-Tuesday.

The only bit of good news is that the humidity will not accompany the heat until Tuesday or Wednesday at the earliest.

NAM Temperature forecast for Monday, predicting a 1pm temperatur of over
36 degrees Celsius or 97+ degrees Fahrenheit

At least the humidity won't be around until Tuesday-Wednesday: the NAM
model predicts us to be at about 30% humidity at 1pm Monday.

Showers, Storms on Tap for Thursday...

2007-07-05T11:13:00.000-05:00

After a crazy 4th of July, things will settle down a bit today. While the northern D.C. area is still under a slight risk for severe weather, given the lack of instability from all of the cloud cover, I do not think the area will see much in the way of strong storms today.

With that said, I am confident that almost everyone around the area will see some rain this afternoon and evening. There may even be some thunder or wind in some of the stronger thundershowers, but fortunatly, not much in the way of severe weather.

If any severe weather does arise, we will have updates...

Radar image at 12:30 showing a wide expanse of showers over

the Apalachians... most of the area should see these pockets of

showers/thundershowers this afternoon/evening

TORNADO WATCH IN EFFECT UNTIL 10:00PM....

2007-07-04T13:05:00.000-05:00

7:10 UPDATE: SEVERE THUNDERSTORM WARNINGS CONTINUE FOR MONTGOMERY COUNTY AND PRINCE GEORGES COUNTY IN MARYLAND...

Discussion: Most of the severe weather, particularly the tornado risk has diminished... EHI values have droped below 2 across the area after peaking at about 3.5 around the 4pm time. This means that most of tornadic activity (3 separate reports of funnel clouds, 1 reported touchdown) has ended.

However, as radar continues to indicate, there are stil a number of thunderstorms that have to cross the immediate metro area in the next several hours. With that said, I do expect the fireworks on the mall to go on as planned, but earlier shows across the area may be in difficulty.

If you are south of the city, I think you are completely done with the thunderstorm risk, but north of the city, periodic thunderstorms will continue for the next several hours.

5:00 UPDATE: TORNADO WARNING FOR SOUTHERN LOUDOUN, NORTHERN FAQUIER, AND NORTHERN PRINCE WILLIAM COUNTY.

A number of spoters reported a funnel cloud with the storm moving through northern Montgomery County. Also, one spotter recorded 1.5 inch size hail! So yes, take these warnings serously!

For those of you planning of going down to the Mall tonight, please stay put until at least 7pm when this line hopefully has moved through the district.

4:30 UPDATE: TORNADO WARNING FOR NORTHERN MONTGOMERY COUNTY... People planning on attending firework displays in the evening (7-10pm) should really think twice before going. Hopefully, we can get these dangerous storms out of the area before 9pm.

4:00 UPDATE: SEVERE THUNDERSTORM WARNINGS REMAIN IN EFFECT FOR NORTHERN MONTGOMERY, SOUTHERN FREDERICK, NORTHERN FAQUIER, AND CLARK COUNTIES. People in the immediate DC metro area should expect in increase in thunderstorm coverage by 6 PM.

As I had anticipated yesterday, the NWS has issued a tornado watch for the entire DC area until 10:00 tonight.

People should be very careful before planning to go to any 4th of July celebrations around the area, and should listen to any additional warnings as they are issued...

July 4th Bombers...

2007-07-03T10:26:00.000-05:00

This morning, I am getting increasingly concerned about the chances for strong storms that may interfere with 4th of July evening celebrations across the D.C. area. My concerns are in line with the NWS, which went ahead and extended the slight risk area for severe storms tomorrow to include the immediate western subburbs of the District.

The flow aloft tomorrow will be from the Northwest while at the low levels, the flow will be from the southwest. That will lead to increasing shear and the potential for supercells to develop that can support tornadoes and large hail.

Why do we always show the lifted indexes? Because Storms needs enough lift

to rise to 45,000 feet + for them to be of concern. Tomorrow evening, lifted indexes at 7pm (shown) will be at about -4, meaning that at 500 mb, a parcel of air will be 4 degrees warmer than its environment (meaning that it will keep rising).

The dangers Wednesday are not associated with the cold front (we will have to worry about that Thursday) but the warm front. Warm fronts are less likely to spark squal lines, but carry a greater risk for tornadic activity. We can show this on a Energy Helicity Index (EHI) Plot (below). These plots measure the risk a given supercell has at becoming tornadic--- and tomorrow the risks are relatively high. While this does not mean we are going to have a tornadic outbreak tomorrow evening, people should check local radars, watches, and warnings before heading out (or just check out the blog!).

EHI values at 7pm tomorrow are expected to be at about 2 in the

city, and 3+ in the western subburbs--- meaning that any supercells

that develop run the risk of spawning a tornado

Drier Air Moving in... Storms Return for 4th-5th

2007-06-30T13:44:00.000-05:00

The same front that sparked our severe weather on Thursday has been very slow in getting out of the area. However, it looks like drier air will finally start filtering into the area tonight and into tomorrow (below).

NAM model for Sunday, showing humidity at about 20%!!!

As for the work week, it looks like the heat and humidity will return (like that's new) for Tuesday, and really get bad for the 4th of July. We will need to watch the chance of storms for the 4th, as moderatly unstable air will meet an approaching cold front. I don't believe that we will see a wide-scale severe weather event on the 4th due to an absense of sheer in the atmosphere--- but spotty storms may be possible.

The real interesting day this week appears that it will be Thursday, where there may a significant severe weather event...stay tuned.

SEVERE THUNDERSTORM WATCH IN EFFECT UNTIL 11:00 PM...

2007-06-28T14:38:00.000-05:00

The National Weather Service has issued a severe thunderstorm watch in effect for the entire D.C. metro area until 11:00 tonight...damaging winds will be the biggest threat.

A sqaul line appears to be developing in Central Pennsylvania (below) and may cross the area in the early evening. Ahead of this line, a couple of isolated strong storms may pop up through 6pm. Stay tuned for updates....

STRONG STORMS TODAY, MORE TOMORROW

2007-06-27T12:30:00.000-05:00

2:20 UPDATE: SEVERE THUNDERSTORM WARNING FOR PRINCE GEORGES COUNTRY IN CENTRAL MARYLAND UNTIL 3:15 EST.

A highly unstable airmass combined with a slow moving cold front will begin to spawn some strong thunderstorms this afternoon and moreso tomorrow.

One small pop-up storm already caused some small hail over Eastern Fairfax county at around 1:30pm today--- and more additional storms are possible later this afternoon.

Additional updates will be posted if watches/warnings are issued.

Radar image at 1:34 showing the dying stages of the thunderstorm

over Eastern Fairfax county and additional storms building over the

Appalachians and Northern Maryland.

Pleasant weather to dominate...

2007-06-20T12:16:00.000-05:00

Temperatures for the remainder of the week will remain in the low to mid 80s, under mostly sunny skies with low humidity. While there is a slight chance for a storm Friday, for the most part, D.C. weather will be wonderful the next several days...

Satellite image taken Wednesday showing the last of the
clouds from the cold front moving out of the area, and drier more
confortable air moving in.

SEVERE THUNDERSTORM WATCH IN EFFECT UNTIL 11:00 PM...

2007-06-19T15:46:00.000-05:00

11:00 UPDATE: Severe Thunderstorm watch has expired... there may be a couple of isolated strong storms later tonight, but the main threat has diminished with little rain or damge to speak of from earlier today.

5:00 UPDATE: SEVERE THUNDERSTORM WARNING FOR NORTHER MONTGOMERY COUNTY AND FREDERICK COUNTY UNTIL 5:30 EST

Strong storms have developed across the area and have prompted the National Weather Service to issue a Severe Thunderstorm Watch for the entire D.C. metro area until 11:00 EST.

Discussion: A developing line of storms along I-81 will strengthen and slowly push north and east. While there may be a couple of storms ahead of this line, the main threat to the area will come later this evening around the 6-9 time frame..

Severe Thunderstorms possible Tuesday

2007-06-18T20:44:00.001-05:00

With temperatures expected to climb well into the 90s tomorrow, a round of strong storms is possible. The most likely areas to see severe storms are the northern suburbs of the D.C. area.

A strong cold front will approach the area and provide the lift for the storms, as indicated on the lifted idexes forecast map below. While there may be a couple of scattered storms in the afternoon time period, several computer models indicate that a squall line will develop and cross the area as shown on the NAM model forecast (right) in the late evening hours.

(Above) NAM model forecast for the late evening hours Tuesday showing a squal line extending from Eastern Canada to the northern suburbs of D.C.
Damaging winds are usually the most dangerous risk with squal lines.

(Above) Lifted indexes are projected to be in the -4 to -5 range in the afternoon and evening hours. Note: lifted indexes are a measure of the instability in the atmosphere...

>0: any thunderstorm development is unlikely
0 to -3: Severe thunderstorms possible but not likely
-3 to -6: Severe thunderstorms possible
-6 to -9: Severe thunderstorms likely
<-9: GET OUT!

Heat to return...

2007-06-15T22:30:00.000-05:00

With an onshore breeze, temperatures hit
just 69 degrees on Wednesday and 70 yesterday. However, winds will shift to the south and west as we head into the weekend pushing temperatures into the 80s and near 90 by Sunday.

The heat will continue to surge into early next week, with a number of weak systems skirting to our north. While there may be a brief relief from the heat with the passage of a weak cold front on Wednesday-Thursday, long-term models continue to show dangerous heat and humidity for the remainder of the month.

The 18z NAM model for Sunday--- showing temperatures in the area hitting 90 degrees and more heat building west (above).

GFS model showing temperatures getting close to the 100 degree mark on the 26th and 27th of June (above and right).

Warming Up for Father's Day

2007-06-14T19:57:00.000-05:00

Tonight and Tomorrow:
Temperatures tonight should be seasonably pleasant, dipping into the mid 50s around DC, to near 50 closer to the Maryland state line. Showers will become more of a threat later tomorrow afternoon as a another upper level disturbance slides southwestward from Newfoundland. High temps tomorrow should be able to sneak into the lower to mid 70s under mostly cloudy skies.

Extended:
Temperatures by Father's Day will likely soar into the 90s as an area of high pressure slides to our south, transporting warm and humid air into the region. After Sunday, however, a general cooling trend is expected, and temperatures should return to near normal levels by early next week. A cold front is expected to cross the Mid Atlantic Wednesday afternoon, and will further lower temperatures into the lower 80s.

Image: Several members of the Short Range Ensemble Forecast Model (SREF) predict high temperatures near 90-92 degrees on Sunday afternoon. The average (bottom right) is near 88-90 for the immediate metro region.

Image courtesy of the Penn State E-Wall

107th US Open Weather=Fantastic:
While the weather for the first round of the 107th US Open at Oakmont Country Club wasn't quite ideal, mother nature should cooperate nicely for the remaining three rounds of the Open Championship. Temperatures will hover just around 80 degrees Friday, Saturday, and Sunday, and skies should remain mostly sunny to party cloudy. Very isolated showers may develop just east of the Pittsburgh, PA area, but should not be a threat to play.

Cooler Weather The Rest of the Workweek

2007-06-13T15:06:00.000-05:00

Currently:
A few showers and thunderstorms are presently traversing areas south and west of the immediate DC metro area. An intense, severe thunderstorm currently over Herndon and Fairfax in Virginia produced nickel to quarter size hail in Reston, and will affect Manassas and Manassas Park within the next 30 minutes to an hour.

Regional forecast models do indicate the potential for the main line of severe storms (currently located in Central Pennsylvania) to propogate southward into central Maryland between 6 and 8 PM tonight. If this does ocurr, and the line maintains most of its intensity as forecast, areas from DC northward would likely experience a second wave of showers and thunderstorms before things die down with the loss of daytime heating.

Tomorrow through Friday:
Temperatures tomorrow should only rise into the lower 70s partly to mostly cloudy skies. Any precipitation appears unlikely at this point.

Low temperatures Thursday and Friday nights will range from 56 in northern areas of Maryland to 63 in places like Fredericksburg and central Virginia. Obviously, the air conditioner can get a brief rest before near to slightly above normal temperatures slide back into the region for the weekend.

Saturday and Sunday:
Under sunny skies, temperatures on Saturday and Sunday will rise into the mid and upper 80s across the Mid Atlantic, and we may even break 90 on Sunday as winds swing around to the southwest, funneling warm air into the area.

Large Earthquake Strikes off Guatemala:
According to CNN and the USGS, a large, 6.8 magnitude earthquake struck just off the coast of Guatemala at 3:30 PM Eastern Daylight Time. Due to the quake's depth, distance from land, and overall magnitude, damage will likely remain relatively minimal and aftershocks and tsunami are not a threat.

Image courtesy of the USGS Hazards Program of Northern California

Yet Another Severe Thunderstorm Event

2007-06-13T14:25:00.001-05:00

3:15 UPDATE: SEVERE THUNDERSTORM WARNING FOR MONTGOMERY COUNTY IN MARYLAND UNTIL 3:30 PM.

More isolated severe storms will likely develope over the next several hours.

Severe Thunderstorm Watch in effect until 9pm EST for the entire D.C. metro area with the exception of extreme southern Virginia south of Fredericksburg.

Discussion: Same setup as yesterday. Unseasonably cold mid-level lapse rates will again make damaging hail the main risk. Expect the main cluster of storms to move over the area in the 5-7 pm time frame.

Satelite imagery showing the storms developing over nothern Pennsylvania with the center of low pressure off the New Jersey coast

Severe Thunderstorm Watch in Effect until 8PM EST

2007-06-12T13:55:00.000-05:00

8:00 Update

Severe Thunderstorm Warninds in effect for: Culpeper, Rappahannock, Stafford, the city of Fredericksburg, and Spotsylvania Counties in Virginia

Discusion: All of the severe activity has cleared the D.C. metro area...

Clinton, MD reported 2" size hail at 6:17 PM!!!

5:15 PM UPDATE:

Severe Thunderstorm Warnings in effect for: Montgomery, Talbot, Queen Anne's, and Western Dorchester Counties until 6PM

Storms are approaching the DC metropolitan region, moving in a pecuiliar fashion to the south and southwest (usually, storms in the Mid Atlantic travel west to east) at about 20-30 miles per hour. Expect thunderstorms with heavy downpours, wind gusts 40-60 mph and cloud to ground lightning to move inside the beltway within the hour.

Severe Thunderstorms are firing east of the Chesapeake Bay over Talbot and Queen Anne's counties and should move into southern St Mary's county in two hours or so.

Above Image: Radar at 5PM shows thunderstorms moving southwest towards the District. Some of the more intense storms contain small hail. (GRLevel3)

--Previous Post
The air mass over us has become moderately unstable this afternoon with temperatures well into the 80s. Additionally, unseasonably low freezing points will make damaging hail the main threat with these storms.

Expect the main complex of storms to move over the area around the 6-7 pm hour.

Stubborn Closed Low to keep us Unsettled

2007-06-10T16:27:00.000-05:00

**Note: A new member--John Yarchoan--has joined DCweather.com and will add posts from time to time. We are also planning on adding a "weather wars" section in which we both battle over temperatures and weather forecasts**

An offshore closed low seen on visable satellite (right) will keep the D.C. metro area unsettled for at least the first part of the work week. While we are not talking about a washout, scattered showers and thunderstorms are possible on Monday and even more likely on Tuesday and Wednesday. On a positive note, due to a lack in upper level winds, any shower or storm that may pop up in the afternoon hours has the potential of dropping a solid quarter to half an inch of rain, and thus may help us make a dent into the rainfall deficit. Also, temperatures will strugle to get out of the 70s for much of the week.

The closed low seen off the coast of Cape Cod (above)

The problem can be more clearly identified if we take a look at the 500 mb chart (left). A small disturbance which is what is left from the severe thunderstorm outbreak across the east on Friday is being forced between the troph from the closed low and a developing ridge across the deep south. When this happens, unsettled weather often takes control. The pattern will stay in place at least until Wednesday because as the disturbance drifts south, it will drag the closed low with it.

This can best be seen on the 500 mb chart for Wednesday. In this frame, the disturbance as strengthened and drifted south to a position around Mobile, AL. As it has done so, it has forced the closed low south and west, thus continuing to give us unsettled weather.

500 mb chart for Monday (top) and Wednesday
(bottom) showing the closed low across the
Northeast and a weak disturbance drift from
the Ohio River Valley to the deep south .

Images courtesy of Unisys Weather and NOAA

Changeable Spring Weather

2007-04-04T19:36:00.000-05:00

A Freeze Watch is in effect Thursday Night through Saturday Morning

Temperatures over the past few days have been averaging out well above normal. In Washington, Reagan National Airport eclipsed 80 on Monday for the first time this year, but all of this is rapidly coming to an end. Across the United States, the months of March and April signify the coming of volatile and rapidly changing weather patterns--from severe weather outbreaks, to late-season snowstorms, to flooding rains, all of which have been present for the past few days.

A massive storm system, which originated from a Pacific Upper Level wave of energy about 12 days ago, is responsible for the major severe weather outbreak that ravaged the Midwest and Southeast yesterday, blizzard and severe winter storm conditions to the North, and flooding rains to the south. This same storm system ran a cold front through the region today, and will drop temperatures into the mid 40s for highs by the end of the week (see image at right)

Low temperatures are expected to dip below freezing tomorrow night, which is why the National Weather Service has issued a Freeze Watch for areas east of the Blue Ridge Mountains. Any trees or flowers that have already begun to bloom due to the unseasonably warm air as of late have the potential to be damaged or killed in the cold weather.

Image above: 15 hour forecast image from this afternoon's run of the WRF-NAM numerical weather model valid Thursday mid-morning. Notice the surface temperatures hovering just around freezing in the Mid Atlantic.

Image courtesy of the PSU E-Wall

Late Season winter-storm battering the Northeast:
The same storm system responsible for the severe weather in the Midwest and the significant cold blast in the Mid Atlantic is also bringing a heavy, wet snowfall to portions of New England and the Upper Midwest. Driving through Williamstown, Massachusetts was a chore today (looking at colleges), as freezing rain and sleet covered roadways at higher elevations. A changeover to snow will occur later tonight, and snowfall totals of 3-6 inches are in the forecast over the next 24 hours.

Further to the north and east, snowfall totals are expected to range from 6 to 18 inches across Vermont, New Hampshire, and Maine.

Wintry Mess for the Workweek

2007-02-24T13:14:00.000-05:00

Winter Storm Warning DC North and West 4AM Sunday to 4AM Monday for 1-2 inches of snow/sleet accumulation and 1/4 to 1/2" of ice.

Freezing Rain Advisory DC South and East 4AM Sunday to 4AM Monday. Up to 1/5" ice accumulation possible.

After a fine, but chilly, Saturday afternoon, clouds will begin to increase from the west overnight as a developing storm system rotates into the upper Mid West. Latest visible satellite imagery reveals a large expanse of cloud cover in the heart of the Continental United States and a clearly defined cold frontal boundary slicing through eastern Oklahoma and Texas.

All of this is headed eastward, being steered by a 100-110 mph jet stream.

The forecast over the next 48 to 54 hours is incredibly tricky--just like the majority of winter storms this season.

Precip onset:
The North American Mesoscale model brings isentropic precipitation (ie, overrunning precip) into the DC metro region shortly after 7AM as does the GFS. So, I am confident that a wintry-mix of freezing rain, sleet, and snow overspreads the District between 7 and 10 AM.

Precip Type:
Probably the most uncertain aspect of this storm. It appears that cold air will not be quite as strong as it was during the last winter storm, as high pressure is situated in the Hudson Bay in Canada. Nonetheless, a strong Cold Air Damming signal is present in forecast models as cold air bottles up east of the Appalachian Mountains.

The image to the right is a skew-t plot of temperatures and dewpoints. It's basically a vertical slice of the atmosphere, but the isotherms (lines of equal temperatures) are skewed from right to left. By 7PM Sunday evening, the GFS is clearly the warmer of the two models. If the GFS were to verify at this time, all of the frozen precipitation in the District will have turned over to plain rain. The NAM, on the other hand, is much colder, and still barely supports frozen precipitation.

I believe most of the precipitation (say, 80-90%) will be frozen, that is, either freezing rain, sleet, snow, or a mixture of all three. It will start as as snow with possibly a little sleet mixed in. By Sunday evening, enough warm air has intruded into the upper atmosphere to turn everything over to freezing rain.

This may turn out to be a fairly significant ice storm for the region, primarily north and west of the District. Places in St. Mary's county or southern PG county will likely go above freezing Sunday evening and Monday morning, turning everything over to plain rain, limiting ice accumulations.

The morning rush on Monday may be significantly impacted by this winter storm.

Clipper drops Snow; Rain is the next Threat

2007-02-18T18:48:00.000-05:00

Potential Weather Hazard:
A powerful storm system is expected to develop in the Midwest by next weekend, and will likely bring heavy rainfall to the region early next week.

Tonight and Beyond:
After a nice period of moderate snow earlier this evening associated with a Clipper system, skies will begin to clear, allowing temperatures to dip into the mid and upper teens. Gusty northwest winds will combine with the cold surface temperatures to produce wind chill values in the single digits.

Tomorrow, mostly sunny skies and diminishing winds will accompany high temperatures in the upper 30s to near 40 degrees to the south. Winds overnight Monday will then turn to the southwest, ushering in moisture and warmer temperatures ahead of a developing weak storm system that will pass to our north on Wednesday.

Rain showers should begin to overspread the immediate metro region between 2PM Tuesday afternoon, and 8PM in the evening. Showers will continue off and on through the night, before tapering from west to east Wednesday morning and early afternoon.

Sunday afternoon run of the WRF/NMM numerical weather model revealing rain showers in the region late Tuesday night. Image courtesy of PSU E-Wall

Significant Rainfall a Possibility Next Week:
A more significant storm system (appears it will be a rain system at this point), is forecast to move into the region next Sunday. An intense area of low pressure looks to develop somewhere in the Midwest on Saturday before rotating northeastward into southeastern Canada. A few models develop a scenario in which the DC metro and/or Mid Atlantic area experience torrential rainfall and the possibility of severe weather before the frontal passage.

Stay Tuned.

Chilly weather to Remain

2007-02-16T16:27:00.000-05:00

Cold, Windy, and Still shoveling out:
Even with the region's latest snowstorm long gone (in fact, it's become quite a snowstorm for Nova Scotia and eastern Quebec), bone-chilling weather lingers across the Mid Atlantic and Northeast. Winds gusting upwards of 30 mph in some locations are creating wind chills in the low to mid teens, with below zero readings in extreme western Maryland and southwestern PA.

Due to the significant amount of sleet and freezing rain that accompanied this week's storm, temperatures in the low to mid 30s and an increasing sun elevation have failed to do much in the way of melting the wintry mess. This has forced many local school systems to shut down for the third day in a row, much to the delight of students around the region. Look for temperatures to moderate somewhat tomorrow afternoon under partly cloudy conditions. High temperatures should reach into the upper 30s and lower 40s across the area, with the exception of areas in northern Maryland, where temperatures will struggle to break the freezing mark.

A Clipper System for the weekend:
A rather vigorous clipper system, seen on regional satellite and radar, is currently rotating southeastward out of the Midwest, accompanied by snow showers as far south as the Oklahoma border.

Numerical models have been locked on to this latest wintry system for the past few days, and spread light snow showers into the northwestern suburbs late tomorrow afternoon and evening. Most of the time, clippers have a very difficult time spreading precipitation into the immediate metro area because of the moderately tall peaks of the Appalachian Mountains, which act as a sort of brick wall. This factor, coupled with the already moisture-starved system, usually spell "no snow" for the District.

However, it appears that this latest clipper will dive far enough south of the Capital to spread light snow showers into the metro region late tomorrow night. Dry air is abundant at the surface, but I think precipitation will gradually be able to work through this impediment through the night. Expect generally less than an inch of snowfall accumulation with this system.

Snowstorm Post-Mortem:
This week's snowstorm was, bluntly, one of the more difficult forecast that have faced area meteorologists this season. Marginal surface temperatures, disagreeing computer models, warming mid layers (which brought freezing rain and sleet into the forecast) all lead to a very challenging winter forecast.

Generally, I think my forecast worked out pretty well in most locations. Granted, I did not expect such significant ice accumulations across south central Maryland, where upwards of half an inch to three quarters of an inch of ice accrued on almost everything. The higher forecast snowfall amounts in northwestern MD did not verify (where I had envisioned 6-12" of snow, only about 6-8" accumulated in very isolated pockets).

All in all, however, my forecast verified pretty well in most areas, including the District, where 2-3 inches of snow, sleet, and freezing rain accumulated. My "all snow line," on the other hand, was completely off, as freezing rain and sleet made it all the way into southeastern New York and Northwestern PA.

The image at right is the total snowfall/ice map with data from the local National Weather Service office in Sterling, VA. The pinkish line represents where significant ice accumulations occurred. Areas within the pink area received anywhere from .5 to .75 inches of freezing rain.

Overall subjective grade: B-

Exciting Times--Potential for a Major East Coast Storm

2007-02-10T17:29:00.000-05:00

Monday Evening Update:
18z Numerical Model Guidance run this afternoon would seem to favor a slightly colder scenario for the DC metropolitan region. Previous runs turned precipitation over to plain rain Wednesday afternoon as a warm nose of surface air shot northeastward. However, the 18z GFS run was slightly colder around the region for the duration of this storm, certainly a good sign for winter-weather lovers.

Still, for those of you who enjoy snow, you're probably going to have to wait for the next storm (if there is one). The snow currently falling across the area is associated with an upper level disturbance out ahead of the main weather system currently sitting in northern Texas .

Very little in the way of accumulation is expected tonight in the immediate metro area. Temperatures will slowly fall into the upper 20s and lower 30s.

----Previous Post-------

Potential For Significant Snowstorm in Mid Atlantic:
After a brief hiccup in the numerical modeling of this latest winter storm (OOz run of the Global Forecast System painted and absolutely horrific snowfall forecast for the region), guidance seems to be on track once again. The Latest GFS run pumps out close to 1.25 inches of liquid precipitation, which, under the standard 10:1 snow to rain ratio, would yield a 12 inch snowfall for the region.

While there are still significant differences in the vertical temperature profile of the atmosphere during this event, I have enough confidence to outline potentials with this potential storm.

I am confident that light to moderate snow will break out across the region from west to east sometime late Monday night or early Tuesday morning. This precipitation will be associated with warm air in the upper levels sliding over a dense dome of cold air near the surface.
The second part of the storm, likely the most significant sow-maker for us, should arrive sometime Tuesday night into Wednesday morning.
All Precipitation should exit the region by Wednesday night

Precipitation-Type Issues:
From a climatological standpoint, major winter storms rarely finish without some kind of precipitation change-over, either from snow to freezing rain, or from snow to sleet, at least in the Mid Atlantic. The North American Mesoscale Model (NAM), which honestly does not perform that well at 84 hours, is indicating the potential for a change-over from snow to sleet early Wednesday morning as low pressure systems get cranking to our south.

The GFS is much colder, on the other hand, and keeps all of the precipitation in the form of snow from DC north and west. Areas closer to the Bay in Southeastern Maryland will likely change over to a mixture of rain/snow/and sleet on Wednesday.

If the snow does in fact change over to sleet and/or freezing rain, snow totals would be significantly lower than if we managed to remain all snow. At this point, I think the majority of the storm will be snow, but I cannot rule out the possibility that areas as far north as Hagerstown change over to sleet at some point during the storm.

Even with the usual disparity among computer model guidance, there is a relatively high risk of a significant winter event in the Mid Atlantic early next week. I am very confident that a snowfall of at least 4 inches is in order for the Washington, D.C. metropolitan region.

Technical Thoughts

2007-02-08T17:49:00.000-05:00

Below are my technical thoughts from last night. Little has changed in my thinking with respect to next week's potential winter storm:

Twenty-Four day 500mb upper air analysis from 00Z February 2 reveals a weather pattern dominated by a large positive PNA ridge that, at some points, stretched almost all the way to the North Pole. A massive polar vortex has remained relatively persistent over southern Canada, driving very low atmospheric heights into the CONUS. Currently, 500mb height anomalies are around -350 to -360 meters over the Canadian Maritimes.

The aforementioned positive PNA ridge has slowly been trending towards a more neutral state as successive upper lows rotate towards the Pacific Northwest. Nonetheless, it appears as if near normal to slightly below normal temperatures will remain the norm over the northeastern portion of the country for at least the next week or so as the PV spins over eastern Canada.

12Z Ensemble GFS/MREF members reveal very similar solutions through at leas the next 144 hours. A piece of upper air energy looks likely to eject northward from the Laptev Sea within the next 36 to 48 hours and attempt to partially phase with the current Polar lobe over Newfoundland. This new polar low will likely play a significant part in a potential major winter storm for the Southeast and Mid Atlantic states early next week.

As mentioned above, most GFS/ MRF ensemble members seem to agree (uncharacteristically at such an extended range) on some sort of modified Miller A low pressure system developing in the south central United States next Sunday evening/Monday morning, with a large area of isentropic lift and associated precipitation developing along and to the east of the low pressure center. The aforementioned polar low that should traverse the North Pole in the next few days will likely aid in suppressing the potential storm system far enough south to keep the precipitation-type for the immediate metro region primarily snow.

Synoptically, the surface set-up looks to closely resemble that of the President’s Day snowstorm of 2003, which dumped upwards of three feet of snow across the region. While this storm does not look to be accompanied by as strong a 500mb low, the surface set-up is very similar, which, along with the almost unanimous model support from the ECMWF/GFS/MRF/CANADIAN models, leads me to believe there is a very good potential for a significant winter weather event in the Mid Atlantic next week.

Granted, the cosmetics of this storm are very uncertain at this point, as they would be with any potential storm over 5 days out, but signs are pointing in the snow-lovers’ favor. I am a little concerned with the set-up of the PNA ridge and NAO, which has basically been positive the entire winter, as well as the position of the polar low in southern Canada (which may build so far south it shunts precipitation south of the region), but these concerns will be smoothed out as time progresses. Needless to say, this system bears very careful attention over the weekend.

Get Ready for An Arctic Blast

2007-01-22T17:50:00.000-05:00

Snowfall around the region was fairly light with this recent storm. Most locations received between a trace and 2 inches of snow with a thick layer of ice to top it all off. What snow and ice did melt today will refreeze slowly tonight, as temperatures fall only a degree or two below freezing by morning. However, any secondary roads that have not been cleared yet will pose a problem tomorrow morning as ice freezes within tire treads. (I'm currently thinking areas south of DC will not dip below freezing, but just touch the 32 degree mark overnight).

Our attention then turns to a new system developing off the eastern Seaboard during the middle of next week. At this point, most models show a low pressure center forming about 400 to 500 miles off shore, which would limit any precipitation potential around the region. However, I wouldn't rule out the possibility of a few flurries or light snow showers Thursday evening and into early Friday.

Above: Snowfall Map for the January 21-22 storm. Snowfall totals from the National Weather Service in Sterling, VA and Mount Holly, NJ.

Very Cold Airmass to Settle in within two weeks:
The coldest air of this winter season will likely descend upon the region in about 8-10 days as a massive polar vortex rotates southward into the Eastern United States. The image below depicts this scenario:

The image on the left is today's 500 mb Geopotential Height from the European Model run valid between the next 7 to 10 days. In other words, the map you see there is the average of the aforementioned model's forecast 500 mb heights for the three day period between the 30th and 1st of February. Notice the massive "blob" of purple and blues covering almost the entire US from coast to coast. This is a region of well below-normal heights, and hence, below normal temperatures. The image on the right is the best correlation I could find for this upcoming weather pattern--January 18th, 2003. The +PNA ridge is evident in both images (the large ridge of high pressure bisected by the west coast) and the Geopotential Heights are nearly identical.

High Temperatures on that day in Washington were in the 20s, with morning lows in the single digits and low teens, while temperatures in the Northeast only managed to rise into the lower teens for highs.

Finally, the image on the right is the latest GFS (Global Forecast System) Ensemble 850 mb Temperature anomalies valid next Tuesday evening. Notice the large pool of -8 to -12 degree Celcius anomalies engulfing the Eastern United States during this period.

If all goes as currently predicted, the entire eastern half of the United States will see below to well-below normal temperatures in about 8 to 10 days. High temperatures may hover around the lower 20s in the Mid Atlantic.

Old Man Winter Returns

2007-01-16T16:09:00.000-05:00

After over a month of above average temperatures, a massive arctic front has finally swept through the region, bringing temperatures down below average. Most computer models show Washington getting up to about 40 degrees or so tomorrow afternoon, which would put the high temperature below normal for the first time this month.

After the cloud debris associated with this cold front push east out of the region, a large dome of high pressure should move into the region for 24-36 hours, yielding mostly sunny to partly cloudy conditions Wednesday and into the evening. Once the high moves offshore, a coastal storm is expected to develop about 200 to 300 miles east of the eastern shore which has the potential to spread rain and snow showers into the metro region Thursday night and early Friday morning.

Things get a bit more interesting next week as signs point towards another low developing in the vicinity of the Appalachians next Sunday night and Monday. Temperature profiles are iffy at this point, but there are some indications that this next system could bring a mixed bag of precipitation (rain, snow, and/or ice) to the metro region.

Oppressive. Hot. Brutal.

2006-08-02T14:33:00.000-05:00

The region is baking once again as the sweltering heat wave of 2006 rolls on. Check out temperatures across the East Center United States (see image at right). Air temperatures in most locations have soared into the upper 90s...and the harsh thing is--those aren't even the heat index temperatures. Factoring in the humidity in the air (currently running at around 35-45%), it feels like it's well over 100 degrees in many locations.

Washington, DC may possibly break its record for highest temperature today--100 degrees--but the thermometer needs to jump up two more degrees very quickly, before the sun begins its decent. At 4PM, the temperature at Reagan National weather a stifling 99 degrees with a heat index of 106.

Elsewhere around the region, the records for both Dulles and BWI will likely remain intact. The high temperature at BWI looks like it will top out around 98 degrees, and Dulles should top out around 97 degrees.

Relief is coming...
A cold front currently draped across the Upper Midwest is slowly making its way eastward. There is a noticeable drop in temperature behind the front, with many locations reporting temps in the upper 70s and mid 80s. This front will close in on the region tomorrow afternoon, and should traverse the region on Friday, dropping the temperatures a good 10 to 15 degrees for the weekend--a welcome bit of relief from the heat!

Surface Analysis courtesy of the HPC

However, with the prospect of more comfortable weather comes the threat of severe storms. There is a slight risk that a few severe storms bubble up during the afternoon, mainly northwest of the region. A little better shot for more organized thunderstorm activity moves in on Friday.

Tropical Troubles...
Tropical Storm Chris continues to churn just north of the Leeward Islands with 65 mph winds and a central pressure near 1007 mb--quite high for a storm of his strength. Chris looks disorganized on visible satellite images (see right) with convection being sprayed to the east by 10 - 20 kt easterly wind shear. Nonetheless, Chris is expected to intensify into the first hurricane of the season, and may pose a threat to the western Gulf Coast in the near future.

Image courtesy of the National Hurricane Center

Ugly Summertime Weather

2006-07-29T16:31:00.000-05:00

EXCESSIVE HEAT WATCH EFFECTIVE FROM TUESDAY AFTERNOON THROUGH THURSDAY AFTERNOON. Heat index values will likely exceed 110 degrees in many locations.

Sultry Weather not going anywhere soon: After a brief respite from the intense DC summertime weather last week, the hazy, hot, and humid weather known all to well to Washingtonians has returned once again. Temperatures over the past three days have once again soared into the mid 90s. By most standards, high temperatures in the 90s would be bearable, but adding in a touch of tropical air makes it feel incredibly sticky and uncomfortable, and more of it's on the way.

The bubble of extraordinary heat that had been plaguing the desert Southwest for over two weeks finally receded yesterday as a trough slid in from the west. Now it's our turn to feel the heat as a dome of anomalously high heights in the middle and upper atmosphere slides eastward, and proceeds to bake the Eastern half of the country. All indications point towards a ramp-up in temperatures through the next four to five days. Temperatures by Tuesday will likely hit the triple-digits, and this combined with dewpoints approaching 80 degrees may produce heat indices eclipsing 110 degrees!

This portion of the National Weather Service Special Weather Statement outlines the potential hazards of heat this extreme:

THIS BUILD UP OF HEAT COULD MAKE HEAT-RELATED ILLNESSES A SERIOUS THREAT...ESPECIALLY FOR OLDER GROUPS...PEOPLE WITH ILLNESSES...AND PEOPLE LIVING IN NON-AIR CONDITIONED HOMES. NOW IS A GOOD TIME TO BEGIN PREPARING FOR A HEAT WAVE ACROSS THE REGION THROUGH MIDWEEK.

With the heat comes the potential for thunderstorms on a daily basis (called diurnal thunderstorms due to their predilections to bubble up during the heating of the afternoon, and die out after sunset). Tiny, isolated thunderstorms are popping up across the region, moving in a slow southeastward track towards Central Virginia (See image top right, courtesy of WUSA 9 News Weather). These storms will persist for a few more hours before dissipating after sunset.

Temperatures should moderate by the end of next week, but will remain in the mid to upper 80s before a trough approaches the region in 7-8 days. And there's some more good news: The average high temperature in DC peaked last week at 89 degrees, and will continue to fall as we get closer to Autumn. The NWS forecast high temperatures are plotted above (purple) for the next seven days. Notice the "cool down" by the end of next week as we return to near-normal temperatures.

Are Hurricanes Really increasing in Intensity?
I have long been skepticic of the whole "global warming is making the hurricanes stronger" theory. Granted, I believe in anthropogenic warming, but don't think it has happened on a scale large enough to effect hurricane intensity like many have suggested (at least not yet). A recensnippetit in the Washington Post outlined the fact that manscientiststs hold as fact: that hurricane intensity was underestimated for a long period of time while satellites were being developed.

Very few satellites were floating around in space during the 1960s and 70s, and those that were sampling data were doing so at very low resolutions. A satellite would have to view a hurricane at an angle, and this combined with the low horizontal resolutions, lead to misinterpretationon and misrepresentation of hurricane intensity. Now, with the so-called hi-res satellites, and the development of an technique to objectively analyze hurricane intensity (Dvorak Technique), hurricane intensity measurements have gotten better, which, I think, has a lot to do with the stark increase in the number of intense hurricanes we're seeing worldwide.

Image courtesy of the Georgia Institute of Technology

It is a proven fact that the number of hurricanes has remained relatively constant around the globe over the past 30 to 40 years, even though the number of intense hurricanes (Category 3 or higher) has nearly doubled. In my opinion, it is much easier to say "hey, that's a hurricane" on even the lowest resolution satellite images, than to distinguish between a 110 mph Category 2 Hurricane (not considered Intense/Major), and a 115 mph Intense, Category 3.

3 H's return for weekend

2006-07-14T16:44:00.000-05:00

Currently:
Showers and thunderstorms associated with an upper level disturbance to the west (which will move into the region over the weekend) will persist for a few more hours before pushing southward into Virginia.
Thunderstorms will be capable of producing brief, heavy downpours given the presence of a tropical airmass.

Temperatures should fall into the mid-70s overnight in a sticky atmosphere.

Hazy, Hot and Humid:
After a relatively cool start to the month of July (temperatures are averaging slightly below normal), the hazy, hot, and humid days of a typical Washington, D.C. afternoon will make a comeback starting this weekend. Tomorrow, a weak surface low will track through the region, setting off showers and thunderstorms, primarily during the afternoon around the metro region.
By Sunday, as the low exits off the East Coast, a massive upper level ridge developing in the West will punch into the region and turn the oven onto "broil." High temperatures on Sunday will likely nose into the lower 90s, and with dewpoints hovering around 70 degrees, you can bet it will feel absolutely miserable outside. But that's just the beginning...

All indications at last check revealed that temperatures would continue to rise through the beginning of next week, likely approaching 100 degrees by Tuesday as the core of the upper level ridge moves overhead. Some computer models show high temperatures peaking at around 100-102 degrees on Tuesday afternoon as dewpoints near 75 degrees. In this case, heat indices would exceed 113 degrees, significantly increasing the threat for heat exhaustion and heat stroke, especially in the elderly.

The new look of Districtweather.com:
I was tired of the previous districtweather.com layout, and decided to get to work on another template. The nav bar at the top isn't functional, but you will see things begin to fall into place gradually over the next few weeks.

I have a summer job at the NASA Goddard Space Flight Center, which isn't giving me much time to update this website, but I will try to keep this blog updated as much as possible.

Washout!

2006-06-26T19:29:00.000-05:00

After the record-breaking rainfall experienced last night, we're once again caught in the middle of a miniature War zone along the east coast. A quasi-stationary frontal boundary (warm and cold front collide and stall) is draped from New England all the way down into Florida, and this combined with copious amounts of tropical moisture surging northward from the Western Atlantic has produced flooding rainfall across much of the Mid Atlantic.

Intense bursts of rainfall will intermingle with lighter but steady rainfall as independent bands move northward from Virginia. Expect anywhere from 2 to 6 more inches of rainfall before everything finally makes its way out of the region by Friday.

Even with the passage of this stationary front by the end of the week, little ripples in the upper atmosphere may initiate showers and thunderstorms over the weekend.

Stay up to date with the latest traffic information at Maryland Department of Transportation's website

First Full Day of Summer Yields Oppressive Heat

2006-06-22T14:43:00.000-05:00

**FLOOD POTENTIAL**

Isolated thunderstorms and heavy showers across the region have started flooding in several areas. Thunderstorms are moving very slowly, and are dropping copious amounts of rainfall in the isolated places they are ocurring. Through the night, be prepared for flooded roads, especially in low-lying or hilly terrain.

On this first full day of summer, temperatures have soared into the low 90s under partly sunny skies and a breezy northwesterly wind. The good news is that dewpoints are relatively low--hovering around 60 degrees--which isn't adding too much of that sticky feeling outside.

Severe Weather
While widespread severe thunderstorms are not anticipated, the Storms Prediction Center has placed parts of the region under a slight risk for severe thunderstorms. Surface Based CAPE-- which is a measure of how unstable the atmosphere is, and, hence reveals how likely thunderstorms are to become severe--is very high, ranging anywhere from 2000 to 3000 Joules/Kg. Thunderstorms thrive in this kind of setup, so any storms that manage to fire later today have the potential to produce damaging winds and small hail.

Washington D.C.'s PGA Tour Stop:

The Washington areas only PGA tour event settles in at the TPC at Avenel. The Booz Allen Classic (Once called the Kemper Open) is being played today just down the road from Congressional Country Club.

Conditions will remain warm through the tournament, with a 20-40 percent chance of a shower or thunderstorms in the afternoon. Spectators might want to bring a small umbrella just in case.

The HEAT INDEX measures the combination of humidity and temperature at a given location. The index reveals what it feels like to the skin outside, and any values over 95 can be dangerous. Heat Indicies may briefly reach 95 or so at the tournament today, but expect slightly cooler conditions tomorrow.

Cutoff Low Creates dreary Springtime weather

2006-05-11T09:17:00.000-05:00

Overview:
A storm system that has been plaguing the Midwest for the past few days has finally moved east and has brought low clouds and scattered showers to the region.

Current radar reveals widely scattered showers stretching from north central Maryland down towards the DC metro region. Overall, expect a dry but dreary Thursday afternoon. If you plan to venture out, take the umbrella just in case.

Right: WJLA radar showing light and widely scattered showers around the DC metro region.

The system that is responsible for this change in weather--from the magnificent sunny afternoons to the boring low overcast--is a cutoff low. This is simply an upper level weather system that gets "stuck" so to speak in the mean wind flow.

This is an example of an cutoff low--in fact it's the one influencing the weather today--on a 500 millibar map. Notice how the height contours are "closed" into a circle around the center of the low. The upper level winds are forced to dive southward around the center of the low, with one jet stream to the south, and one to the north. In essence, the low is wedged in between the two jet streams and cannot move.

Expect the chance for showers to linger through the weekend and into next week. It doesn't look like we'll be getting a break until Wednesday of next week (at the earliest). Just note, it this weekend will not be a washout, just expect a few showers here and there.

Happy Easter

2006-03-25T18:35:00.000-05:00

The Next Few Days:
It's been over three weeks since I've made a post, so I figured it was high time I made another one.

Very thin bands of rain showers have developed over the region in response to energy upstream in the Ohio River valley diving southeastward over the Appalachian Mountains. These showers are part of the same weather system that has brought over 40 tornadoes to the Midwest over the last three days.

Scattered light showers will continue overnight and into tomorrow morning before upper level energy swings around the base of another upper low near Newfoundland. Depending on how the said energy moves around the upper low to the north, showers may continue through the day tomorrow, or come to an end around 8 or 9 AM north of DC. Whatever happens, however, bring the umbrella along if you're heading out anytime tomorrow.

By Monday evening, drier surface and midlevel air will slide into the region, scouring out any remaining showers and cloud cover.

Drought Woes Increasing

2006-03-23T18:41:00.000-05:00

Dry Stretch of Weather:
Over the past few weeks, an excessive drought has developed over the a majority of the East Coast, and weather records indicate the last time measurable precipitation fell over the region was about 20 days ago on March 2nd (which registered only .03 inches of liquid at National).

The Climate Prediction Center's "Drought Monitor" is registering abnormally dry conditions over much of coastal New England and the Mid Atlantic, which severe drought is expanding to the southwest. (That would probably explain why my backyard is dominated by a malignant brown grass.)

While sporadic chances of rain and snow are in the forecast over the next two or three days, coverage should be minimal, and precip totals would likely amount to less than a tenth of an inch.

That said, expect a 30ish percent chance of a sprinkle or two tomorrow, with a little better chance of precip on Saturday, especially east of the I-95 corridor.

Dust-Bowl out west
And while it may seem like our mini-drought is bad enough here, the drought taking place out in Oklahoma is much worse. The entire state has been declared a Natural Disaster Area by the US Department of Agriculture due to the extreme drought taking place in the Central Midwest.

Thoughts of Snow Douse Spring Fever

2006-03-20T10:16:00.000-05:00

Spring arrives at 1:26 this afternoon (when something called the vernal equinox occurs), but with cloudy skies and cool temperatures, spring fever will be put on hold for awhile. A developing storm system to our southwest will continue sliding northeastward through today and tonight.

Temperatures should fall into the lower 30s before precipitation moves into the region tomorrow morning. Snow showers will progress across the region in a southwest to northeast fashion between 7 and 10 AM.

Time permitting, I may be able to get a snowfall map out later today, but don't count on it. Because temperatures over the past few days have been sitting in the upper 40s/near 50, road temperatures are well above freezing, which should inhibit snowfall accumulation on the major arteries. However, secondary roads will likely become slick through the afternoon, but snowfall accumulations should stay under 1 or 2 inches on the back roads.

The NWS seems to have a good handle on this situation, and explains in their Forecast Discussion that the Precip forecasts would justify a few inches of snowfall accumulations (like 4 or 5" if taken literally), but mitigating factors like road surface temperatures and above-freezing surface temps should keep totals down around 1-2 inches. Out west, however, where temperatures should be a bit cooler, snow accumulation may eclipse 3 inches in some locations.

Image above: Satellite Picture showing a developing baroclinic leaf in the central US.

Winter 'Aint Over

2006-03-16T10:32:00.000-05:00

A reminder of Winter
A weak wave of upper level energy will zip overhead tonight and tomorrow, which should spread rain showers into the area. After midnight or so, the surface should have cooled sufficiently to allow snow showers to dust the region with March's first snowfall. Accumulations will mostly be confined to grassy and elevated surfaces (the roads should remain fine).

Another, more intense area of low pressure should make an appearance later next week. Surface temperatures will once again be marginal for accumulating snowfall, but it's interesting we can go from sunny, 80 degree days, to snowy, 40 degree days in less than a week.

Electric Bill Woes:
As 9 News reports on its website: "For Marylanders, Summer Could Be Hot, Dark And Expensive," tensions between lawmakers and electric company's have begun to strain. Pepco is reporting:

Due to significant increases in the cost of fuels used to generate electricity, the average monthly electric bill for Maryland residential customers will increase by about 38.5 percent, or $39.00; residential bills will rise from an average of $101.29 today to an average of $140.29 once the June 1 price increases are fully reflected in customer bills.

BGE electric will also increase rated by nearly 80% come summer, which is an extra $800 a year.

Furthermore, if this summer turns out hotter than normal, further strains will be placed on the electric company's to supply power to the Capital Region residents.

Source: PEPCO and WUSA9 NEWS

Wow, It's Kind of Hot

2006-03-10T17:32:00.000-05:00

Weather Record

Did you think it was warm yesterday? Well, a record high of 78 degrees was set today at Reagan National Airport, breaking the previous record of 77 set back in 1964.

Tonight and Tomorrow:
Clouds will continue to stream in from the north and west as the sun sets, associated with a diving Canadian trough. Low temperatures should remain in the lower 50s for the most part as daytime radiation gets trapped under the cloud cover. A small, 20 or 30 percent chance of an isolated shower will persist through the night.

Tomorrow, a warm front will lift north of the region, allowing the temperatures to once again soar past 70. Any showers (or thunderstorms) that develop tomorrow should be few and far between, but be aware there will be a small chance of showers tomorrow afternoon.

Is Winter really over?
I have been cautious to post the "winter cancel" messages even with the prospect of 70+ degree weather for an extended period of time. Lo and behold, the GFS, NOGAPS and Canadian models all show some signs that would point towards another cold and snowy period developing late next week. Granted, the synoptics and upper-air pattern are not ideal for a major snowstorm, but GFS precip progs are impressive to say the least.

Surface temperatures would most likely inhibit snowfall accumulations (but it would be nice to see some snow before winter shuts its doors).

Evening Update

2006-03-08T20:41:00.000-05:00

Tonight and Tomorrow:
A small 30 or 40 percent chance of showers will persist through the night a developing low pressure system throws a warm front our way. By early afternoon, the said warm front should have pushed north of the region, conveniently placing us in the warm sector, as winds swing around to the southwest, and draw warm, tropical air into the Mid Atlantic. High temperatures tomorrow will likely break 60, and a few readings around 65-69 wouldn't be too surprising.

Friday
By Friday morning, a cold front will near the Appalachian Mountains, and the chance of showers (and a few thunderstorms) will increase once again. Any showers/thunderstorms that manage to develop will be few and far between, which is why precip chances are relatively low (around 30 or 40 percent).

Image: Precip Forecast from the MM5 Model valid Friday afternoon

Windy Weekend Weather - Spring in Sight?

2006-03-04T18:49:00.000-05:00

Today was just one of those days when you either wanted to be inside drinking some hot chocolate and watching a little basketball, or bundled-up outside enjoying the crystal clear skies. For those that chose the latter route, there was no denying the fact that it was kind of windy today. Gusts to 30 or 40 mph were not uncommon, which brought the wind chill down around freezing for most of the day. A high temperature of 47 will go in the books for Washington, DC which is about 5 degrees below normal.

Tonight and Tomorrow:
Winds will subside somewhat tonight, although it will still remain breezy. Temperatures will drop into the mid to upper 20s under clear skies, while wind chills plummet into the teens.

Tomorrow, winds will once again increase towards sunrise (Gusts 15-25 mph) as temperatures rise into the upper 40s.

High cirrus clouds should begin overspreading the region late tomorrow afternoon and towards nightfall as a clipper-like system drops down from Canada.

How we stand on Snowfall this Season:
With meteorological spring underway, I decided to take a look back at snowfall around the region for the Winter of 2005-2006.

At Reagan National Airport in Southeastern DC:
Observed Snowfall: 13.6"
This time Last year: 12.5"
30-Year Average: 15.2"
Departure from Normal: -1.6"

At Dulles International Airport in Loudon, County:
Observed Snowfall: 14.7"
This time Last year: 17.3"
30-Year Average: 21.2"
Departure from Normal: -6.5"

At Baltimore/Washington International Airport:
Observed Snowfall: 19.6"
This time Last year: 18.0"
30-Year Average: 18.2"
Departure from Normal: +1.4"

To the snow-lovers around the region, it may appear as if this winter has not lived up to forecasts (probably due to the fact that no snow fell during January), but in reality, this winter has been "average," and will likely verify within most long-range predictions.

Talk About the Weather:
Weather guru's Justin Berk and Tony Pann (from 9NEWS) will duke it out tomorrow on the popular Weather-Talk Radio show in Baltimore, MD. This weeks topic is Global Warming and a few other things:

Will the models bust on this weeks storm?
The rumors of a large trough and east coast storm in early March.
7 Day Battle
Week in Review
Weather Music Posted online After This Show

Tune in tomorrow at 3:05-4:00 PM at 680 AM or, stream the show from this link.

Cold and Dry--Two Words That Don't Go Together

2006-02-28T18:20:00.000-05:00

5 Day Outlook

Tonight:
Variable cloudiness tonight as a very weak upper level disturbance slips through the region. There's a very slim chance (something like 25 or 30%) that a few light snow showers stumble into the region later tonight. No accumulation anticipated. Temperatures by sunrise tomorrow will be in the upper 20s/lower 30s.

Wednesday:
Mainly sunny conditions expected with a slight increase in cloudiness towards evening. Highs will climb towards 50 degrees.

Thursday:
Mainly cloudy, especially before noon as low pressure organizes and spreads northeast form the Ohio River Valley. Showers will remain likely until mid afternoon Thursday. High temperatures should manage to break into the upper 50s (possibly hitting 60) before a cold front races through overnight.

It will likely be a bit breezy Thursday afternoon as the cold front nears the Metro Region.

Friday:
Breezy conditions during the afternoon Friday, and high temperatures will likely remain in the mid to upper 40s.

Saturday:
Expect mainly sunny skies through the day and high temperatures in the mid 40s.

Sunday:
Mainly sunny to partly cloudy conditions. High temperatures in the low to mid 40s.

Snowy Future, or just an illusion?
Lately, there's been some chatter going on about the potential for a "wintry-mix" kind of scenario early next week for the big cities along the East Coast. The computer models have been hinting at the possibility of some cyclogenesis somewhere off the Southeast coast next week, but all differ on the position, strength, and timing. The GFS has been sort of consistent in developing a low off the southeast coast during the Monday night/Tuesday timeframe, but this solution appears a bit suspect at this point.

This is something to watch, but at this point, model data would not support an East Coast snowstorm. Still, a lot of the models are failing to correctly analyze upper air features, blocks, wind flow, etc, which adds a certain amount of "insecurity" to the forecast.

Sunday evening Update

2006-02-26T20:37:00.000-05:00

Temperatures today were at their lowest since the 12th thanks to biting northwesterly winds drawing in chilly arctic air from Canada. Officially, the high at National peaked at 36 degrees after a low of 27 early this morning.

Tonight and Tomorrow:
Surface winds will continue to gradually diminish overnight as an area of high pressure slides into the Southeast. Temperatures tonight will drop into the upper teens out to the west, and lower 20s around the city.

Tomorrow, expect off and on cloudiness through the day as an area of upper level energy gets spit out south central Canada. Any precipitation (and it would be snow) should stay on the western sides of the Appalachians, but light snow showers cannot be ruled out overnight Monday.

A stark warm-up is in sight Wednesday and Thursday as southwesterly winds at the surface and aloft pull warmer air into the region. Mid to upper 60s are not out of the question Thursday.

More cold air to Come

2006-02-22T17:19:00.000-05:00

After a fairly prolonged period of moderate to heavy snow this morning, all precipitation has ceased around the region, and we will be left with mostly cloudy conditions over night. I have to admit, however, the snow was a nice little treat (at least for those of us not traveling on the highway).

By the time you wake up tomorrow morning, temperatures will have slipped into the mid 30s and skies will have begun clearing from west to east.

Massive Cool Down:
While the temperatures over the next two or three days will by and large be above average, a massive arctic intrusion (likely the most intense of the winter season) will make a move on the region Sunday and Monday, as a large dome of high pressure slides southeastward from the Canadian Provinces. I think GFS forecast high temperatures Monday through Wednesday are too low given the strength and position of this incoming polar vortex-which is basically a region of excessively below normal atmospheric heights, and below normal temperatures.

I can see highs on Tuesday struggling to break the freezing mark in most locations, especially north and west of the District as cold, -15 to -20C air around 1500 feet up slides overhead.

Winter Retreats; Winter storm Photos

2006-02-15T18:00:00.000-05:00

Update:
Models have trended southward with the system for Monday/Tuesday. There is still a small chance for flurries around the region Monday afternoon, but that's about it.

If you thought the weather today was sweet, just look ahead to tomorrow. Temperatures should soar into the upper 50s/lower 60s under partly cloudy conditions as a midlevel ridge sets up shop along the Eastern Seaboard.

Clouds will increase out ahead of a strong cold front during the morning hours on Friday, which will aid in keeping temperatures down somewhat, although, strong southwesterly winds will effectively neutralize this increase in cloud cover by advecting warmer air from the southern states. Expect highs to average out in the upper 50s.

Temperatures over this President's Day weekend will drop of significantly, from the upper 50s into the lower and mid 30s. After Saturday, things get a bit interesting. A frontal boundary will likely stall out south of the District, setting up a strong "cold dome" over the Capital region. A slug of deep moisture is forecast to oscillate northward Sunday afternoon as weak waves of low pressure develop and move along this stalled cold front.

By Monday, there seems to be fairly good model support (at least for this time range) that would suggest an "overrunning" type event occurs, that is, warmer mid and upper level air rides over the "cold bubble" at the surface, squeezing out any moisture in the atmosphere. Depending on where the cold front stalls, how strong the wavlets become, and the position of the high pressure system off the coast, we could be looking at a pure snow event, or an icing event for President's Day.

Snowfall Photos:
Below are a few photos I was able to capture during and after last weekends snowstorm.

Clearing Out in D.C.

2006-02-14T10:09:00.000-05:00

After the one of the largest snowstorm in Washington, D.C. history, we're finally returning to normalcy in the region. Over 330,000 customers lost power due to this storm, in part due to the high winds and hefty snow accumulations on powerlines.

Forecast Verification. Storm Underforecast and mind-boggling snowfall rates:
Yes, we all know the story: this storm was underforecast by most, if not all professional meteorologists and hobbyists around the region, and the entire Northeast for that matter. As snow fell Saturday evening and failed to accumulate on most surfaces, a fierce apprenhension developed amongst forecasters, and the naysayers began babbling about "busted forecasts."

By 10pm, most meteorologists had dropped their snowfall totals down to 3-6 or 4-8 inches after seeing the snow melt on contact. I decided to keep my 6-10 inch call (after upping the totals Saturday afternoon). But never did I anticipate the snowfall rates we experienced over-night Saturday. Rates of 1-2 inches per hour were common, with isolated 2-4 inch/hour bands setting up across the District and Baltimore regions.

Was I consistent with my forecast?
For the most part, yes. I only updated twice to basically shift the totals upwards, but my general thinking on the swath of heaviest snowfall remained the same. Grade here is an A.

Did I communicate the potential hazards of this storm?
I did not foresee the snowfall rates mention above, and failed to fully communicate this storms hazards. I did, however, mention the possibility of extreme snowfall rates overnight Saturday in the post below. Grade here is a B-.

Were the Snowfall Forecasts accurate?
I nailed the swaths of heaviest snowfall from DC north and west, with the highest amounts towards northeastern MD and New Jersey. Even though the totals were far too low, I am actually fairly pleased with the way this forecast turned out. Grade here is a B+.

So overall my grade for this storm is a low A--a very well forecast event by my standards. Granted, the forecast accumulations could have been a bit better, but we all know how mother nature likes to play tricks on us...

More snow in the forecast, or is this it?
While still up in the air, there seems to be an interesting event plaguing the computer models over President's Day weekend. This Friday and Saturday an intense low pressure system will drag a cold front through the region, accompanied by rain showers (maybe a thunderstorm or two).

By Sunday, everything will have cleared the region as colder air drains southward yet again. Between Sunday night and Tuesday of next week, models develop little "wavelets" of low pressure that skirt along the said cold frontal boundary stalled out around the southeast. Depending on surface and mid level temperatures, any precipitation from these lows could produce sizeable snow and/or ice accumulations. Stay tuned...

Winter Storm 2006

2006-02-11T16:09:00.000-05:00

Mother nature is finally re-paying us for the abominable January blowtorch!! After a period of light drizzle/flurries through most of the day, everything switched over to snow about an hour and a half ago as colder air finally made it into the region. You will not see any accumulation on the roadways/pre-treated sidewalks until after 6 or 7 tonight. However, after that, all heck breaks loose as low pressure currently situated in Georgia explodes as it emerges over the Atlantic Ocean.

The heaviest and steadiest precipitation (snow) will move into the region between 11PM and 6AM tomorrow morning as the low really gets cranking over the benchmark (40N, 70W--winter storms that pass over this area are often the most dubious snowfall producers for the East Coast).

Below is an image from a forecasting product known as BUFKIT, (BUffalo's forecasting toolKIT; developed by meteorologists in Buffalo, NY) which lets forecasters objectively analyze atmospheric forecasts from various models, like the GFS and NAM. Notice the high vertical velocities (the rate of upward or downward motion of a particle ) on the right side of the screen. When these areas of high VV's intersect the area of maximum snow growth, (yellow lines), forecaster's can anticipate locally intense snowfall.

Given current model forecasts, analysis, etc. I have upped the snowfall totals across the entire region. A large swatch of 6-10 inches is a good bet encompassing the major cities. I think 12 inches is the absolute maximum snowfall anyone will see around the region, but totals in excess of 12 inches will be possible further up the road in New Jersey and Manhattan.

Finally, snow's back in the forecast!

2006-02-09T17:20:00.000-05:00

Update!!!
Things are on track for what will likely end up being the largest snowfall this season around the immediate Metro area. Snow will break out across the region during the early mornign hours tomorrow. It may begin as a period of light sleet/freezing rain/or plain rain for a short time before the low levels cool. Afterwards, everything looks like snow north and west of I-95.

Winter Storm for the Snow-starved Capital:
We're still too far from the event for forecast snowfall maps, but there are a few scenarios that look at. We know a low will develop around the Gulf of Mexico tomorrow, strengthen rapidly as it moves up the coast, and depart the picture by Sunday afternoon. The intensity of this storm is still in question, but indications are it will be rather significant (sub 990mb).

The track of the low is also important factor in snowfall forecasts. A track too far off the coast would keep the precip all snow, but limit the intensity and overall amounts. A track closer to the coast would significantly increase the snowfall amounts, but mixing of freezing rain, snow, and plain rain would become an issue, primarily south and east of the District.

At this point, I think our chances of a snowfall greater than 4 inches in the immediate metro region are fairly high (maybe 50 percent) through Sunday afternoon. If things continue to pan out, the National weather Service will likely issue Winter Storm Watches tomorrow morning.

Back to typical February cold

2006-02-06T15:36:00.000-05:00

For the first time in nearly 2 weeks, temperatures topped out only 1-2 degrees above normal values (Average high in DC is 43 degrees). This "arctic outbreak" if you want to call it that, comes on the heels of one of the warmest January's on record, featuring high temperatures that would consistently top 60 degrees. Last week, a large lobe of below normal atmospheric heights split off from a stagnant Polar Vortex rotating around the Bering Strait, and spilled into the Central and Eastern United States.

In a previous post I stated:

I believe model forecast temperatures (GFSX, which runs off the GFS model runs at 00 and 12z to forecast surface parameters) are too high next week, in the mid 40s. The strength of this incoming trough would suggest high temperatures struggle to make it out of the 30s by midweek.

Since then, the said model has shown a downward trend in high temperatures through Friday of this week, which would match up nicely to other model forecasts revealing -13 to -15 degree Celcius (-55 to -65F) temperatures up around 5,000 feet. Forecast highs for Wednesday and Thursday have fallen into the upper 30s/and lower 40s.

Computer Models Playing with our emotions:
Late last night, two mid-range numerical models, the GEMGLB and ECMWF both developed a massive sub 980 millibar surface low near Cape Hatteras, NC around Sunday/Monday of next week.

Guess what the 12z runs showed. Nothing. Nadda. In fact, there was no sign of the Hatteras Low, which was instead replaced by a massive 1040mb Canadian High Pressure cell.

It seems like a broken record, and the tune has been played so many times this winter. This is, however, an interesting feature to should be watched carefully over the next few days as the weather pattern we've moved into would certainly support wintry weather at least for the next 2 weeks. (Accuweather seems to be toying with the possibilities...)

Big Weekend Storm; Cold on its way

2006-02-03T10:04:00.000-05:00

Quiet weather for the next 12-24 hours as a low to the northeast departs the United States, and another low forms around the ARKLATEX.
By early tomorrow afternoon, rain showers will once again ride into the region on a screaming 100mph Jet.

By Saturday evening, most of the rain will have departed the region, but upslope snow showers will affect the western slopes of the Appalachians. (Sorry, no snow around the metro region). This storm is significant in the fact that it will finally break the spell of above average temperatures, allowing a massive Canadian trough to dip into the United States.

Image courtesy of: Accuweather.com

Cold Air Invasion:
As this occurs, the cold air that has managed to build up in Canada will finally be let loose, toppling the mild temperature regime over the entire East Coast. I believe model forecast temperatures (GFSX, which runs off the GFS model runs at 00 and 12z to forecast surface parameters) are too high next week, in the mid 40s. The strength of this incoming trough would suggest high temperatures struggle to make it out of the 30s by midweek.

I have been harping about this "pattern change" for awhile now; since mid January and things are still set for a rather quick return to winter in the coming days.

The image at right is the mean 500mb forecast chart from the GFS long range model, and about 10 other members that are run as an ensemble. These types of models and forecasts generally have better accuracy over longer periods of time because they are each started with slightly different initial parameters, like temp, wind, pressure, etc.

A New Month; Hope for Snowlovers

2006-02-01T10:20:00.000-05:00

As we say goodbye to the 7th warmest January on record at Reagan National Airport, there is reason to believe a rather significant cooldown towards mid-month is in store for the region. A massive amount of cold air has congealed north of 55 degrees North latitude, where temperature readings below -20 degrees are prominent.

Over the next few days, possibly by early next week, a chunk of that cold air looks to break off from the main "motherload" and slide eastward towards the Northeastern United States. By mid-late next week, this little cold air intrusion will have increased in scope and size; and by the end of the week, a massive ridge should have set up shop along the Western US--allowing air to flow northward as it hits the west coast, before dipping southward into Minnesota-Oklahoma-Arkansas, and Alabama. In essence, the jetstream that has consistently roared into the United States from the Pacific Ocean will no come onshore towards Alaska, gathering cold air is the 100+ mph winds slide into the Eastern US.

Furthermore, it appears many of the teleconnection indices (like the NAO, PNA, EPO, etc [probably all jargon to you]) are forecast to favor a fairly cold February. In February's that averaged out with a +PNA, and -EPO (current forecasts for this month are for a +PNA, and -EPO), the month was accompanied by temperatures from 2 to 4 degrees below average.

You probably won't really notice a difference in air temperatures until the 10th or 11th, but come mid month, I think we have a great shot at returning to winter.

Punxsutawney Phil's lost his owner:
The furry groundhog that's the oracle of winter forecasting recently lost his 15 year owner, Bill Deely. He said to job ate up too much energy and time. Deely will accompany Phil one last time, for the February 2nd weather forecast--he has a good chance at seeing his shadow.

We're off to a good Start

2006-01-30T10:11:00.000-05:00

The weather today will cooperate for many of you, as clouds scatter out of the region, and temperatures rise into the lower 60s.

Superrefraction and Ducting...Pay attention:
With all the fog this morning, a high moisture content was hovering a few meters off the ground, before decreasing rapidly with height above 100 feet or so. This type of regional weather set up; that is, one with a large amount of ambient moisture close to the ground, and a low amount of moisture a few hundred feet up, creates a phenomenon on Doppler Radar known as superrefraction and ducting. The radar beam becomes bent, and in this case, bent in such a degree as to intersect back with the earth in north central VA. When the radar beam comes in contact with the earth, high reflecitivies are revealed on the radar, known as as anomalous propagation.

Forecast:
A low pressure system will develop overnight before moving up the east coast tomorrow morning. Rain showers will once again overspread the region, lasting through midday, before pulling out by the evening rush. There is a slim chance (better chance in the mountains) that some of the showers change over/mix with snow towards the noon hour tomorrow. No accumulation anticipated.

Long Term Outlook:
As you may have heard, the temperatures in Alaska remain brutally cold (some readings around 50 or 60 below zero). Current indications are that this cold gets set loose within the next 180-200 hours, and coagulate in central Canada for a few days. By the 6th or 7th of February, we should begin to feel the effects of decreasing temps, before plunging into a well below-average temperature regime around the 10th-15th.

Some GFS ensemble members (a specific long-range numerical model) push sub 5280M heights at 500 millibars into the region, which happens to be a considerably low atmospheric height for our area. Normally, temperatures associated with sub 5300M heights at this time of year plunge into the 20s and 30s

Just some good stuff to look forward to...

Bleak close to the Weekend

2006-01-28T20:34:00.000-05:00

The Knickerbocker Disaster
It's hard to imaging that a day when temperatures soared into the upper 50s under crystal-clear skies, is also host to the deadliest snowstorm on record for the Washington, D.C. Metro region. On a particuarly gloomy day 84 years ago, nearly 30 inches of heavy, wet snow had accumulated over the region associated with a powerful Nor'easter, which expelled a pressure roughly around 20 pounds per square foot on the roof of Crandall's Knickerbocker Theater in downtown D.C. At 9PM, the tremendous weight of the snowfall split the theater's roof down the middle, killing 98 individuals and seriously injuring another 130.

Image courtesy of Weatherbook.com

Gloomy Weather tomorrow:
Needless to say, we won't be expecting a 30-inch snowstorm any time soon; in fact, we're expecting just the opposite--rain showers. A powerful jet stream racing through central Mexico and southeastern Texas is pumping tropical moisture northward into the Ohio River Valley. A surface low pressure system will gradually slide northeastward into the Great Lakes region by tomorrow morning. Showers will overspread the region during the early afternoon hours on Sunday, before racing out of the area around nightfall.

As for our *potential* wintry episode next week, things are still up in the air. It's basically a given that a secondary low develops along a stalled surface front Monday evening, but exactly when and where are still issues that have yet to be glossed over.

The National Center for Environmental Protection, the agency that developed the GFS, NAM (formerly the ETA), RUC, and WRF, recently dropped profilers in the North Pacific to give numerical model guidance a better edge in forecasting next week's storm system. (The basic principal behind this being the 'weather' moves in a predominantly west to east fashion following the jet stream, and the drops will allow the models to analyze upper weather features more accurately in tonight's runs). This added analysis data may end up throwing a monkey wrench into ongoing forecasts, but hopefully we can shed some more light on Tuesday's weather potential.

As with all the storms this season, there is no real source of cold air. We usually like to see a healthy high pressure dome in Upstate New York to funnel cold surface air into the Mid Atlantic (guess what, it's not there). So, any cold air will be completely low pressure induced, meaning as the low strengthens, it will have to do so quickly enough to pull colder mid-level air down to the surface before precip moves out of the region.

I'm not wowed by our chances for snow, but it's still there. I would say accumulating snow is out of the picture, but time will tell...

Clear but Cool Close to the Work Week

2006-01-27T10:01:00.000-05:00

Forecast:
After a chilly start to the day, temperatures will quickly warm into the upper 40s/near 50 by mid-afternoon under clear conditions.

For Saturday, temperatures will once again soar into the upper 50s as high pressure propagates eastward, which will turn variable winds to the south. High cirrus clouds will overspread the region during the mid-morning hours, quickly followed by lowering stratus as a developing low skirts the region. Scattered showers should develop towards 3-5PM, although the day will not be a washout.

The chance for showers will remain through Sunday night, before decreasing through the day Monday (although the risk for a passing shower will remain). By Monday night, a surface low should begin developing along a stalled frontal boundary in the southeast, which will deliver a second punch of rain showers to the region overnight and through Tuesday. A few models however, develop this said low into a vigorous nor'easter Tuesday evening as it races northeastward towards the Grand Banks. (Could this mean snow for the region?) The Quantitive precipitation Forecast map to the right (NCEP/NOAA) shows nearly 1.5 inches of liquid-equivalent precip through Wednesday (how much of this, if any, is snow is a coin toss at this point).

The folks at LWX (the National Weather Service office for the Washington's/Baltimore area) also see this potential for a wintry concoction next week:

SECONDARY SURFACE LOW DEVELOPMENT APPEARS LIKELY AS THE SYSTEM MOVES TOWARD THE MID ATLC COAST...INDICATED BY THE GFS/CANADIAN AND ENSEMBLES. THE LOCATION OF THE SECONDARY DEVELOPMENT WILL HAVE A BIG IMPACT ON THE MONDAY NIGHT/TUESDAY FORECAST. 00Z GFS WOULD SUGGEST THAT THE SECONDARY DEVELOPMENT WOULD COMMENCE OVER EASTERN NC. THIS WOULD ALLOW THE COLD AIR TO COME RUSHING BACK SOUTHWARD AND GIVE THE POTENTIAL FOR FROZEN WINTER PRECIP. PREVIOUS RUN IS WEAKER AND FURTHER NORTH WITH THE DEVELOPMENT AND WOULD KEEP PCPN IN THE FORM OF RAIN. FOR NOW HAVE FORTIFIED THE POPS A BIT FOR MON NIGHT/TUE AND HAVE NOT MADE ANY SIGNIFICANT CHANGES TO THE WEATHER GRIDS. SNOW WILL HAVE TO BE CONSIDERED EAST OF THE MOUNTAINS IF MODEL TRENDS CONTINUE.

Needless to say, we'll be watching this system over the weekend, and that forecast confidence--at this point--is minimal at best.

Now this is Winter!

2006-01-25T10:17:00.000-05:00

Quick Reminder of Winter stirs Snow-Lovers:
I must first congratulate meteorologist Tony Pann of 9 News for his forecast made last week. He was able to see the potential wintry weather we experienced last night/today 5 days out. Most, if not all the numerical model guidance killed any precipitation trying to move into the region as it crested the Appalachian mountains. There were a few reports of thundersnow, (just as it sounds; heavy snow in a thunderstorm) in north central Maryland last night, and a band of snow showers raced through the metro region earlier this morning. Kudos to Tony...

Forecast:
Tonight: I don't know about using the word "bone-chilling" to describe the weather as accuweather meteorologists have on this graphic, but you have to admit, the image itself is pretty imaginative. Winds will slacken somewhat overnight as the pressure gradient (see post below) relaxes. Temperatures will dip into the mid to upper 20s under mainly clear skies.

Tomorrow through Saturday: Generally clear conditions through the rest of the week as strong high pressure builds in overhead. Temperatures Thursday will be near average (43), but as the said high moves east, a southwesterly flow will draw warmer air (once again) into the region for the weekend. Highs in the mid 50s on Saturday are not out of the question (another good golfing weekend?). This is supported by higher than normal height anomalies in the central United States that will progress eastward over the next few days.

Sunday-Wednesday:Clouds thicken Sunday afternoon in response to an approaching low. Rain showers look to develop late Sunday night, and last through the day on Monday. A few models suggest some wrap-around precipitation mixes with colder air on Tuesday to throw a few snow showers our way before clearing takes place during the afternoon.

TV Special:
Set your VCR or be ready to watch Doug Hill's special on the highly-hyped introduction of the WeatherBug Network tonight at 8:00 PM. You can tune into this Hill-hosted special on Channel 7 (broadcast) or channel 27 (cable).

Windy weather ahead

2006-01-24T18:17:00.000-05:00

WIND ADVISORY IN EFFECT FROM 9AM TO 5PM TOMORROW. WIND GUSTS TO 50 MPH ARE POSSIBLE BEHIND A STRONG COLD FRONT

Cold Front Pressing forward:
After afternoon temperatures near 50 degrees, a return (once again) to the ever absent "normal" weather is in the offings for the region. A powerful cold front, associated with a developing (and intensifying low) near the US/Canada border, will sweep across the Ohio River Valley this evening, before setting its sites on the metro region overnight.

After the cold front axis passes, you will notice (If you're up at say 4 or 5 AM) the winds quickly begin to ramp upwards. This is caused by a weather phenomenon known as the Pressure Gradient Force, which is defined as:

Therefore, as the spacing between isobars (lines of equal pressure) decrease over a distance, the PGF increases, a figure that is correlated to wind speed. For example: in the image above, the PGF over the Mid Atlantic is something like 1 mb per 100 km, not a very strong one, and therefore, we'd expect generally light winds in the region. However, behind the cold front, the PGF ramps up to about 4 mb per 100 km (rough estimate), and we'd anticipate wind speeds to be significantly higher to the west of the cold front.

So, as the front passes, the PGF will gradually increase, incrementally forcing the surface winds higher as air moves more quickly over a specific region. On top of all this (as if it weren't enough) the release of solar energy as the sun rises has a stark effect on wind speeds. By 7 or 8 AM, the overnight inversion or increase in temperature with height to about 1000 feet, erodes as the surface warms. This allows any quickly moving air in the upper levels to be easily transferred to the surface, further increasing the wind speed. With this in mind, wind gusts to 40 or 45 mph are anticipated tomorrow afternoon.

That's your lesson for the day...

Temperatures should warm above average once again by this weekend.

Welcome back, winter

2006-01-22T11:50:00.000-05:00

For the first time in a long while, it actually feels like January. A strong cold front moved through the region last night, and is currently stalled across the Southeastern US. Moisture associated with a developing low off the Texas coast will slowly progress northeastward over the next 12-24 hours, and clouds will slowly begin to thicken as the day wears on.

Showers are set to invade the region overnight from southwest to northeast. By late Monday, most of the rain shower activity will have moved east of the Mid Atlantic, opening the door to a strong Canadian high pressure cell which will slide into the area during the middle of the week. Temperatures will fall back towards "normal" values, and even slightly below as northerly winds drag cooler Canadian air into the Eastern United States.

Will Winter hold on for February?
The average January temperature at Washington Reagan National Airport [43.5 degrees, 8.6 degrees above average] has moved into 6th place as the warmest January on record, behind 1890 (+8.9), 1913 (+8.7), 1932 (+11.9), 1933 (+7.7), 1950 (+13.1*), and 1990 (+8.7).

For the snow-lovers, most of us have already thrown in the towel and decided that winter cannot possibly make a come-back before March. So, how do February's following extremely warm January's stack up?

In January's where the mean temperature exceeded 6 degrees above normal [1880, 1890, 1913, 1932, 137, 1950, 1974, 1990, 1998, 2002] the February that followed generally featured above normal temperatures; in fact, the average February temperature was 3.4 degrees above the 130-odd year mean. The average snowfall following such January's was meager at best, with an average of 1.3 inches falling at Reagan National, however, there is a caveat:

The North Atlantic Oscillation (NAO), which is the dominant mode of atmospheric behavior in the United States, remained within 1.5 standard deviations from 0 in the aformentioned years. Weakly positive, or weakly negative phases of the NAO generally have minimal impact on the weather in the Eastern US. Most numerical weather models, the GFS in particular, are adamant in developing a moderately negative NAO come February 1st, ranging anywhere from -1 to -4, which would favor colder conditions in the Eastern US.

In short, this is what I'm trying to get at: even though temperatures this month have been ridiculously high, things looks decent regarding a return to winter-like conditions come February, or at least for the first half of the month. There is some troubling data that would suggest the -NAO retreats after the 10th-15th of February, and force temperature back above normal. Still, the temperature forecast for February is on shaky ground. At this point my thinking is temperatures average anywhere from 0 to +1 above normal. Keep your fingers crossed...

What's that...It's January?

2006-01-20T20:28:00.000-05:00

If I didn't know better, I'd be apt to say the weather around here is more reminiscent of early April than late January. So far this month, our maximum daytime temperatures have averaged nearly 52 degrees--more than eight degrees above normal--and high temperatures have consistently popped into the 60s; a rare occurrence in January, to say the least. (Oh, and by the way, Dulles set a new high temp record of 63 degrees today, breaking the 62 degree record set in 1998).

How often is it this Warm
But, how odd is it for temperatures to be this warm, this early in the year? The average monthly temperature (highs and lows averaged) is 34.9 degrees for January. Through the 19th, however, the January 2005 monthly average is a comfortable 7.8 degrees above normal, moving into 9th place for the warmest January on record (in 1st place is 1950, when temperatures for the month average close to 50 degrees, a staggering 13 degrees above normal!)

All things considered, the near record high temperatures we've been experiencing may not be that bad of a thing. Most people I've talked to--even though they crave some of what winter has denied Washingtonians this month--say they've been enjoying the early spring-like weather. Hey, even the golf courses have managed to stay open longer than usual.

There are, however, still signs that colder air makes a move on the region by the end of the month as a negative North Atlantic Oscillation sets up (some guidance suggests significantly low values) which would favor a return to below-normal weather conditions.

Wintry mess tomorrow AM; Colder weather on the way

2006-01-16T16:08:00.000-05:00

A Winter Weather Advisory is in effect for areas north and west of the District from 4AM to 9AM Tuesday morning. Icy road conditions are possible in the warned areas

After the ridiculously windy conditions we experienced yesterday, things have calmed down a bit as we remain trapped between two weather systems--one departing around the Canadian Maritimes, and a developing low in the southeast. Over the next several hours, significant upper level divergence (winds spreading out along a set area, opposite of convergence, where winds converge on a set location) aids in strengthening the said low.

By mid-morning tomorrow, rain showers will have taken over the southeast portion of Maryland, and a potential wintry mix in the northwestern 'burbs as some shallow cold air remains trapped east of the mountains. With this said, there may be a few slick spots on the roadways north and west of the District tomorrow morning.

By Mid-afternoon, the bands of showers associated with a warm front punch north of the region, leaving us in a dryslot for a few hours before a strong cold front progresses over the Mountains. Hefty showers, and a few thunderstorms will break out once again overnight Tuesday and through the morning hours on Wednesday, before everything moves east of the region by 5 or 6PM.

Yet another chance for precip moves into the region next Saturday afternoon as another low develops in the Ohio River Valley.

As for temperatures, daytime readings will generally top out 10 degrees or so above average (in the lower 50s).

Image above right: Futurecast computer model showing the possibility of a little wintry-mix tomorrow morning

Good News for the Snow-Lovers
Over the past few days, a massive Cold Vortex has moved off the Russian coast, and is currently situated a few hundred miles west of the Gulf of Alaska.

This will begin to set the stage for a "pattern reversal" by the end of January as the North Atlantic Oscillation switches over to negative (good for winter stuff in the District), and cold air spills southward in the Contiguous US sometime around the 25th to 27th of January.

The image to the right is the 12z run of the European Model showing a trough developing in the Midwest, cold air spilling southward into the United States, and, more importantly, a Negative NAO as a positive height anomaly sets up over Greenland. It's far too early to pinpoint the potential for winter storms, but the developing pattern would seem to favor a snowy end to the winter season. Cross your fingers...

Snow, High Wind, and Cold

2006-01-14T17:25:00.000-05:00

High Wind Warning in effect 7AM EST Sunday, followed by a Wind Advisory until 4PM EST Sunday afternoon. Wind gusts to 55-65 mph are likely overnight

The highest wind gust I was able to find occurred a few hours ago in Washington, DC with the anemometer clocking a 54 mph wind speed. Surface winds are expected to continue increasing as the night progresses, and a few models pump out wind gusts topping 70 mph.

As the stiff northwesterly winds continue, and radiational heating is lost, surface temperatures will dip into the mid 20s-lower 30s overnight. Current Doppler radar images from Sterling, VA (the Warning Forecast Office for the Greater DC area) reveal a fairly elongated band of precipitation extending from north central Maryland, southward into Charlottesville at this hour. With temperatures falling at their current rates, there is a high likelihood that any precip currently falling as showers turns into snow within the next 1-3 hours.

Any snowfall accumulations are expected to remain below an inch, except out in the mountains, where 2-4 inches of snowfall is expected by Sunday morning.

There's a New F-Scale on the block:
Back in the early 1970s, Dr. Tetsuya Theodore Fujita developed a tornado rating system based on structural damage, at the University of Chicago. This rating system became known as the "F-scale," or "Fujita-Scale" and became a widely accepted damage indicator for the next 35 years.

However, beginning in February of this year, the "old" F-Scale will be replaced by a new "Enhanced" F-Scale that significantly lowers the wind thresholds of all 6 of the F-scale categories.

Below are the previous, and new F-scale rating systems as per the Storm Prediction Center's website:

Old F-Scale:

SCALE	WIND ESTIMATE * (MPH)**
F0	<>
F1	73-112
F2	113-157
F3	158-206
F4	207-260
F5	261-318

New F-Scale:

SCALE	WIND ESTIMATE * (MPH)**
F0	65-85
F1	86-110
F2	110-135
F3	136-165
F4	166-200
F5	Over 200

Image above right: Dr. Fujita, known as Mr. Tornado, was involved in extensive tornado surveys and studies. He invented the F-scale for measuring tornado damage. (Photograph from the University of Chicago Archive.)

Multi-Faceted Storm to Affect the Metro Region

2006-01-13T16:57:00.000-05:00

Severe Thunderstorms, High Winds, and Snow expected over an eventful Redskins playoff weekend

Hold onto your hat's....Literally
For those of you who have been enjoying this mid-spring weather, you're going to be in for quite a shock tomorrow afternoon. Temperatures this week have constantly remained 10 degrees or more above average under partly cloudy skies, but all good things must end, right?

A massive storm system has begun developing in the Ohio River Valley in a "strongly diffluent upper level flow," which is just weather-speak for a rate at which wind flow spreads apart (left or right) of an axis oriented to the normal flow direction; this promotes strong cyclogenesis/low pressure formation and intensification.

Tonight, showers and thunderstorms will gradually increase in coverage as the low and associated cold front approach from the west. Indication are that the atmosphere will remain conducive for nocturnal thunderstorms even after much of the daytime heating has been lost. You often here that "thunderstorms cannot sustain themselves after dark because instability and temperatures have decreased." This is normally the case, but there are exceptions. Case in point, this latest system carries with it such powerful dynamics that strong to severe thunderstorms will likely develop and persist through the overnight hours.

The coldfront associated with this system will race through the region during the morning hours tomorrow, and surface temperatures will fall through the day. By afternoon, the low will have moved east of the region and winds will have begun increasing out of the northwest. Some model data indicates wind gusts in excess of 40-50 mph Saturday night and Sunday.

So here's an overview of impacts this system will have on the region:

Develop Thunderstorms (Some Severe)
Reduce temperatures by a good 30 degrees (by Sunday AM)
Wind Gusts to 40-50 mph
Significant Upslope Snowshowers on the Western side of the Appalachians

I'm not ruling out the possibility of a few snow showers mixing into the rain Saturday afternoon/evening as colder air makes its way into the region. However, most snow showers will be confined to the western side of the Appalachian Mountains where 3-6 inches of snow accumulation will be possible.

Evening Update

2006-01-11T17:45:00.000-05:00

A low pressure system situated northwest of the region is the culprit behind today's nasty weather and coolish temperatures (although, we were still nearly 8 degrees above normal for this time of year--we've just been spoiled rotten by the 55-60 degree weather as of late).

Those of you looking for spring-like weather are in luck-skies are expected to clear within the next several hours, and temperatures look to soar towards 60 ddegrees for the second time this week! We may have to stumble through a bit of early morning fog tomorrow, but this should all burn off by mid morning as incoming solar radiation warms the lower levels.

We basically have two days to catch our breath before a very potent mid-latitude low pressure system makes an approach on the region Friday night. Latest model indications indicate the potential that precip hangs around the region through Saturday afternoon as cold air marches eastward over the mountains. If enough low level moisture can remain around the metro region Saturday afternoon as temperatures fall under still northerly winds, the lagging precip may change over to a brief period of snow.

No matter what happens, however, winds will increase dramatically as this storm system departs. Wind gusts to 30 or 40 mph aren't out of the question, and you may hear your windows rattling overnight Saturday.

Now why Can't it Snow like this in DC?,

For the past few weeks, several snowstorms have blasted parts of Japan with 10-13 feet of heavy snow. The death toll, as reported by the Washington Post, has risen to 71. The main cause of death has been linked to roof failure under the tremendous weight of the snow. What a sight this would be in the Nation's Capital...

Really Pleasant January Weather

2006-01-09T10:36:00.000-05:00

Old Man Winter has decided to take an extended vacation from the Capital region, and for the first time in a long while, I was able to walk around outside in shorts, DURING JANUARY! Even though a cold front associated with a clipper low to the north passed through the region last night, temperatures will still manage to crawl 5-10 degrees above normal this afternoon.

Temperatures yesterday were able to top 60 degrees for the first time since November 29th of last year. While we won't be enjoying weather quite like yesterday's, temperatures today will still manage to crack 50 in most locations under partly sunny conditions.

Graphics courtesy of Accuweather, and PSU E-Wall

OUTLOOK:
On Wednesday, A developing area of low pressure in the Ohio River Valley should begin spreading low clouds and showers over the region by the early afternoon hours. I don't expect anything too severe tomorrow--mainly scattered, light rain showers. High temperatures should remain in the mid-upper 50s.

Thursday through Friday things clear out as we sit in between storm systems developing in the west, and departing lows over the Atlantic Ocean. Temperatures will take advantage of the increased solar radiation, and we will likely approach, if not top 60 degrees once again Thursday and Friday afternoon.

After this, things become quite interesting as many models develop an extremely intense cyclone in the Ohio River Valley once more over the weekend. Draw your attention to the image to the right. This graphic is what forecasters call ensemble model forecasting. Every numerical model has some sort of ensemble member forecast, and the images at right are those of the Global Forecast System (GFS) model.

This forecasting method was developed to improve medium and long-range numerical weather forecasting. Each run of the same model are started with slightly different initialization parameters (time, temperature, wind, etc.) to produce a forecast. If, at the observation time, all of the ensemble members are in reasonable agreement, the forecaster has better confidence in the forecast.

So, the graphic on your right is a host of negative, and positive perturbations (i.e. models where the physical properties of the atmosphere were changed slightly) of the GFS model at 102 hours valid early Saturday morning. As you can see, there is general model consensus of the placement and strength of an intense low pressure system affecting the region during this timeframe. But, as is normal at 100+ hours, there is some uncertainty regarding precipitation placement/onset times.

With this data, I can make a somewhat confident forecast for the weekend. Most of the ensemble members draw extremely warm/humid air from the Gulf Coast northward into the Mid Atlantic (notice that pink line jutting northward towards the Mid Atlantic, that's the 50 degree isotherm about 10,000 feet up in the atmosphere). Showers and thunderstorms will likely break out across the region late Friday night/Saturday morning, before exiting quickly during the evening hours.

Strong, northwesterly winds behind the system on Sunday will promote near normal, to slightly below normal temperatures in the upper 30s.

Closing out the weekend: What's Next?

2006-01-08T18:39:00.000-05:00

While we didn't close the weekend on a high note (chilly mid 40s weather under cloudy skies), all signs point towards an increase in air temperature over the next few days as the polar jet (pJ) is shoved northward into Southern Canada.

The Next Few Days:
Current indications suggest an anomalously warm airmass will move into the region this week, setting the stage for maximum temperature readings in excess of 10-20 degrees above normal!

I had to do a double-take looking at the weather models this evening when I saw forecast maximum temperatures peaking at 60 degrees tomorrow afternoon. A massive high pressure system off the East Coast will turn the winds around to the southwest, drawing in some of the record-breaking warmth in the Midwest. Expect variable cloudiness tomorrow with some clearing during the late afternoon as high temperatures peak in the upper 50s/lower 60s (that's about +15 above normal).

A weak cold front should traverse the region overnight Monday, shifting the southwesterly winds around to the northwest.

Tuesday: Some upper level moisture looks like it will make its ways into the Mid Atlantic on stiff westerly winds, inducing mostly cloudy conditions, and keeping high temperatures generally shy of 50 degrees.

Overnight Tuesday, a warm frontal boundary associated with a developing low in the Ohio River Valley will attempt to push north of the region. Some widely scattered showers may break out across the region after 3 or 4 in the morning.

Wednesday: Given our proximity to a rather large swath of moisture making its way northward from the Gulf of Mexico, it seems prudent to warrant at least a chance of showers through the day under cloudy skies. High temperatures will hover in the mid to upper 50s.

Thursday: There is a little model disparity during this timeframe. A few models suggest the moisture associated with the said low "hops" over the Appalachian Mountains, effectively bypassing the metropolitan region, and leaving us with partly sunny conditions. A few other models, on the other hand, suggest precip lingers around the Mid Atlantic even through Friday.
At this point, I don't feel safe going with a completely dry forecast Thursday. I expect some showers to mingle with the region during the early morning hours, before gradual clearing takes place during the afternoon. If this forecast pans out, high temperatures will likely soar into the upper 50s/near 60 once again.

Channel 4 Launches New Weather site:
Thanks to dcrtv.com for pointing this out. Channel 4 (NBC) recently released its "beta" version of their so-called Weather Plus webpage. You can gather a host of neat information and graphics from this new site, like local forecasts, local doppler radars, cloud/precip forecasts, and localized weather conditions.

Say Goodbye to the Warm weather--For a day

2006-01-06T10:19:00.000-05:00

The warm weather has quietly exited the stage, and yielded the floor to a more seasonal airmass today. A cold front slid through the area (sans fanfare) last night, turning our southerly winds around to the northwest. This northwesterly wind will slowly begin draining cooler air into the region overnight tonight, as low temperatures dip to their lowest values in nearly 15 days, (projected low tonight is 25, and the last time we hit that number was back on December 25th).

Winds will also remain active today, and some gusts to 20-25 mph will be commonplace until nightfall.

Where's the Snow?
While December averaged nearly 4 degrees below normal 30 year values (43.2/47.0), this was primarily due to an excessively cold period during the beginning of the month. Even though we are barely through the first week of January, we are nearly 7 degrees above average for the month. Troughs have consistently affected the region, but a lack of blocking (something to hold the trough's in place) has been all but absent. Thus, the troughs and associated cold snaps move out to sea without introducing the really "cold" wintertime temperatures needed for DC snowstorms. The cold air is then known as being transient as it lasts for a short period of time before progressing eastward in the mean upper level flow.

Furthermore, the overall structure of the jet stream favored storm tracks either too far south of the region, or too far east to deliver any measurable snowfall/precipitation.

But fear not snow lovers. There are some signs that would point to a progressively colder pattern developing towards the end of January. How cold it gets is still up for grabs, but I'd keep an eye on the weather forecast at the end of the month.

Blizzard of 1996:
For those of you who were in DC 10 years ago today, you may remember one of the most historic snowstorms in recent memory, not only for us, but for folks all around the northeast. Although conditions never really made it to "blizzard criteria" around the Capital, it came close.

Anywhere from 15-30 inches of snow fell between the 6th and 8th of January crippling travel around the region for the entire week.

I figured, if we can't get snow now, we might as well look back on memories of a historic snowstorm.

Image courtesy of Ray's Winter Storm Archive

We're Replaying the Old Record Again...

2006-01-04T10:02:00.000-05:00

While the danger for extreme fire weather continues in the Lower Plains, flooding continues to rage in California, and snow falls in the intermountain west, we're left with nondescript weather along the East Coast (save the folks in the Northeast where over a foot of snow fell through Tuesday). I am not enthusiastic talking about this type of weather, and it's beginning to feel like I'm a broken record.

Today: Clouds will hang tough as low-level moisture remains stagnant over the Mid Atlantic. High temperatures will be only slightly higher than yesterday--in the mid 40s.

Tonight: A weak low pressure system approaches the region from the northwest. There is a very small chance (less than 20%) a few sprinkles/light showers make it into the region. Temperatures will dip into the lower to mid 30s.

Clouds will finally begin scattering out over the region on Thursday, after a large cold front sweeps through the region. Temperatures on Saturday look like they will remain in the mid-upper 30s under partly sunny conditions.

Tropical Storm ZETA giving forecasters a hard Time:
Zeta, the 27th named storm of this incredible Hurricane season, developed back on December 30, and continues to defy physical parameters set by numerical weather models. Forecasters at the Hurricane Center have been scratching their heads over this feature in the central Atlantic, as exhibited by Dr. Richard Pasch's discussion written yesterday afternoon:

ALTHOUGH A WEAKENING TREND SEEMED IMMINENT EARLIER TODAY...AS THE LOW-CLOUD CENTER STARTED TO BECOME EXPOSED...A NEW BURST OF DEEP CONVECTION SUBSEQUENTLY REFORMED NEAR THE CENTER. ZETA HAS THUSFAR REFUSED TO WEAKEN IN...WHAT APPEARS TO BE...A STRONGLY SHEARED ENVIRONMENT. CLEARLY WE NEED AN INCREASED UNDERSTANDING OF INTENSITY CHANGE FOR SYSTEMS IN THE SUBTROPICS SUCH AS ZETA...EPSILON...VINCE...ETC.

Zeta had moved into a zone of immensely high shear (change of wind speed with height) that almost always kills tropical cyclones like Zeta. But it appeared, yesterday, the storm had diverted much of the vertical wind shear away from its center, promoting slight strengthening. Zeta is, however, looking quite ragged this morning, and slow weakening is anticipated as Zeta progresses towards Bermuda.

WeatherBug turns to ABC7:
Those of you who check ABC7's weather page may have noticed a "weatherbug network" bar at the top of the page. The WeatherBug corporation dropped its partnership with NBC4, and has moved over to Channel 7. The WeatherBug Corp. is a Germantown, MD based Company, and provides "real time" streaming local weather information around the region.

WeatherBug Features:

Live Neighborhood Conditions & Local Forecasts
World's Largest Weather Camera Network
Real-time Storm Alerts
Top Weather News
Animated Radar and Satellite Images
Up-to-the-minute Temperature on your Task Bar

Doug Hill, and the entire WJLA news team seem to be allotting a significant amount of air time to promote their new friends at WeatherBug. You can download the free 6.1 WeatherBug version here.