Local Forecast
Weather Wars: 7 Day Forecast Battle
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Temperature Verification
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Cold and Dry--Two Words That Don't Go Together

5 Day Outlook

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.

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

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.

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

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

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.
By Lee Carlaw On Tuesday, February 28, 2006 At 6:20 PM

Sunday evening Update

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.
By Lee Carlaw On Sunday, February 26, 2006 At 8:37 PM

More cold air to Come

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.
By Lee Carlaw On Wednesday, February 22, 2006 At 5:19 PM

Winter Retreats; Winter storm Photos

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.

By Lee Carlaw On Wednesday, February 15, 2006 At 6:00 PM

Clearing Out in D.C.

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...
By Lee Carlaw On Tuesday, February 14, 2006 At 10:09 AM

Winter Storm 2006

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.

By Lee Carlaw On Saturday, February 11, 2006 At 4:09 PM

Finally, snow's back in the forecast!

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.

By Lee Carlaw On Thursday, February 09, 2006 At 5:20 PM

Back to typical February cold

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...)

By Lee Carlaw On Monday, February 06, 2006 At 3:36 PM

Big Weekend Storm; Cold on its way

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.
By Lee Carlaw On Friday, February 03, 2006 At 10:04 AM

A New Month; Hope for Snowlovers

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.
By Lee Carlaw On Wednesday, February 01, 2006 At 10:20 AM
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