From the ABC 7 Weather team

Snow Storm Wednesday: Yes, more likely

March 4, 2013 - 03:23 PM
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A "big" snow - at least bigger than we've seen in more than two years - and problems for Wednesday evening commute are now more likely.

3:20 p.m. Monday: The latest probability map from the National Weather Service and the Hydrometeorological Prediction Center shows areas west of D.C., especially the Blue Ridge - Shenandoah Valley region, in the bullseye for 8 inches of snow or more. 

The orange color means an 80 percent chance of 8 inches or more. New complete blog coming soon.

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A Winter Storm Watch will take effect in many areas of the D.C. region starting Tuesday evening.

The Winter Storm Watch encompasses the District of Columbia and every county/city in the Maryland/Virginia suburbs.

Everything I see leaves us still on track for a "big" storm Wednesday.  But the other big risk/threat from this storm is again coastal flooding in New Jersey. 

Everything continues to indicate a "significant," if not major, coastal storm. It will move from the Virginia/North Carolina coast northeast out to sea but winds along the Mid-Atlantic coast could reach 30-50 mph Wednesday afternoon. The dark red areas on the map indicate possible winds of 40-50 mph.

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This past weekend, I said a "big" snow in March in Washington is rare.  The Wednesday storm is now looking more and more likely (70 percent chance, I believe, for the area, especially west and north of D.C.) to be one of those rarities. 

The last time we had 6 inches of snow or more in March was 14 years ago.  So, why am I more confident than yesterday that the Washington area will see a winter storm Wednesday? Continuity, convergence and the cast.

Here's the simulation of the winds and the big wave at the jet stream Saturday for Wednesday:

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and Sunday:

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They're pretty close. You know I don't really fully trust any one model or mathematical/physical simulation of the future weather; I prefer ensembles.

Here is a look at the latest from the U.S. ensemble system showing a storm Wednesday just off the Virginia coast:

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and the European ensemble:

ZZZZZAgain, the models are pretty close, although the dark colors near us also indicate fairly high uncertainty.  Here is a look at the local mid-Atlantic ensembles for the storm track early Wednesday through Wednesday evening from the great weather site at PSU
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What does it show? The cast of characters. Everything has to be perfect staging in the atmosphere if you will for any big snow (or for snow lovers, the "big show") in the Washington area. 

Wednesday will feature cold air for sure, so whatever falls will snow.  But strong winds from the south, southeast and east need to bring in moisture to feed the storm.

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But, as shown in this simulation above of the storm center just southeast of D.C. and air temperature at about 1 mile up, the storm track has to be enough to the south to not allow the mild moist air to win over the cold air. The staging has to be perfect, and remember, the show is still a few days away. Here are my odds for Wednesday's storm

Major snow storm with more than 6 inches in the metro area 70 percent
Morning rain changes to afternoon wet snow in the metro area 60 percent
Heavy wet snow (6-12 inches) north and west of D.C. 70 percent
Rain south and east, ending as 2-4 inches of wet snow 60 percent
A complete miss ~0 perecent

That should bring more excitement for snow lovers, and right now it does look like it will be a wet snow with possible tree damage, power outages and very slippery going for the Wednesday afternoon commute.

Finally, here is the snow probability map from the National Weather Service for snow greater than 8 inches Wednesday.

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This storm will be not only a challenge for us forecasters (here's another great discussion from my friend Wes Junker and the Capital Weather Gang) and you, but a challenge for highway crews also this time because pre-salting won't help. The storm is likely to be a rain-snow event so salt will wash away before the wet snow comes. 

More updates to come but it is still  days now away.  Stay tuned and for more great historic Washington snow storm pictures look at the gallery Steve Rudin put together here.

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