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Posted at 02:07 PM ET, 12/22/2012

Update: Christmas Eve and December 26 winter storm threats


Model runs from the morning of December 22 show low pressure to our northwest late Christmas Eve. Both of these solutions would lead to mainly light rain across the area. The European model indicates that it will be a little colder with the storm further south, but even that solution provides a marginal air mass for snow. (Images: NCEP)
After being absent for all of December through today, the Snow Potential Index made a return. Why? We’re currently watching two storm systems in the coming days — one Christmas Eve and another the day after Christmas (Boxing Day).

The Christmas Eve snow potential has always been low, though some guidance has suggested at least a chance — particularly north and west of D.C. — of seeing some flakes. Much of the newest information seems to indicate the risk is lower than it was before, with the system wanting to track far enough north to keep the area rain. It’s hard to totally rule out a chance of snow though.

Keep reading for more on the post-Christmas threat...


This morning’s GFS model run for midday on December 26th. This solution shows low pressure in the Ohio Valley beginning to “hand off” or transfer toward the East Coast. This run brings the storm track right over the DC area, resulting mainly rain after some frozen precipitation to start in spots. (Images: NCEP)
The bigger ticket item is the Boxing Day storm. This event remains especially tricky to forecast, partly due to the fact that an initial low pressure system to our southwest and west transfers toward the East Coast. Models continue to shift around on this storm, but the risk is still there for a winter event locally. And even in milder scenarios, some wintry precipitation may still accompany it.

CWG Winter Weather Expert Wes Junker addresses the issues at play:

“The models continue to display significant run-to-run differences on the track of the Boxing Day storm. The wide variations between model runs and GEFS ensemble members suggests that it is too early to make a definitive call concerning the storm track or on how much winter weather our area will get.

This morning model runs have trended farther to the west with the storm track and are therefore warmer. There still is potential for winter weather event across portions of the area especially the far western suburbs. Around D.C., it still looks like most of the precipitation will probably fall as rain. However, there is enough uncertainty to not yet rule out the possibility that areas near and inside the beltway might be impacted by winter weather.

This continues to be a storm that we may not be able to provide definitive calls about winter weather until 24 to 48 hours prior to onset.”

To sum up: The Christmas Eve event isn’t likely a notable event, even if it did end up dropping a few holiday-mood-enhancing flakes. The Boxing Day storm has more potential, but is currently fraught with forecasting problems, including signs of a warmer storm locally with today’s guidance. It’s also still 4-5 days out, and that’s plenty of time for small shifts to cause big changes.

We’ll have more on both systems over coming days...

Dan Stillman contributed thoughts to this update.

By  |  02:07 PM ET, 12/22/2012

Categories:  Latest, Winter Storms, Updates

 
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