Outlook:
Regional Satellites and surface observations reveal mostly cloudy conditions across most of the Metro region this hour, as a lobe of upper level vorticity (or "spin" in the atmosphere) that stretches from NY to the Midwest traverses slowly eastward. I expect a majority of the clouds to dissipate later this afternoon as subsidence (sinking air) moves into the area. High temperatures will approach 40 degrees in most locations today under partly cloudy, to mostly sunny skies.

Skies will clear overnight, allowing temperatures to plummet into the upper teens and lower 20s, by sunrise. Be sure to wear a heavy jacket if venturing out tomorrow morning.

A Snowy Christmas?
With Winter officially beginning in two days, thoughts of a White Christmas are prominent among many Washingtonian's. The "official" definition of a White Christmas as defined by the National Weather Service is: "1 inch of snow on the ground during December 25th".

To the right is a graphic (pretty self-explanatory) displaying the probability of at least 1 inch of snow on the ground Christmas Day. The Washington, DC metropolitan region generally does not see a true "white Christmas," but it can happen.

By next Saturday, a developing Clipper Low diving southeastward out of Canada will begin to spread rain (and possibly snow showers) across the metro region. At this point, surface temperatures should remain far too high to support any snowfall accumulation in the Mid Atlantic Region (sorry snow lover's). No White Christmas this year.

An Arctic Re-load in our Future:
Over the past 24 hours, computer models have pumped out colder solutions the close out 2005. A deep trough looks like it will develop by December 27-28th, accompanied by colder conditions, and a stormier weather pattern. Now there's something to look forward to...