RAP 500 mb vort chart

Upper air map Wednesday morning

As the snow melts the threat of flooding rain is on the horizon as the weekend approaches.

This – Wednesday – morning’s low temperatures near the frigid 20 degree mark helped refreeze puddles that hadn’t yet dried from yesterday’s snow melt. Today’s sunshine, although occasionally filtered through high clouds, will continue the melting process as afternoon temperatures boost into the mid-40s around Fredericksburg. A stationary front will be parked across the region today but the air masses on both sides of the boundary are too dry to generate any precipitation.

The graphic shows a very active upper air pattern across the nation that is driving the surface weather. A series of three short wave troughs (labeled #1-3) is shown along the northern jet stream. (The latter feature is flowing west-to-east and is bottling up the really cold air over Canada.) Trough #1 is producing high clouds across northern Virginia this morning as it moves off the East Coast while #2 will kick up more clouds (but no precipitation) tomorrow. Thus Thursday will exhibit more clouds than today for the Fredericksburg area accompanied by temperatures once again topping out in the mid-40s.

The third short wave trough (#3a) is the feature that will dampen Fredericksburg’s weekend weather. It will combine with an upper air low pressure center (labeled #3b) along the southern branch of the jet stream to form a very wet storm system. Indications are that over an inch of rain can be expected in and around the ‘Burg starting Friday and lasting through much of the upcoming weekend. The concern is for local flooding given that the soil will be saturated by melting snow before the rain arrives.

The good news is that the weekend precipitation will all be liquid. The rain looks to begin in Fredericksburg near lunchtime Friday. Meanwhile area temperatures that afternoon will climb to near 50 degrees as warm moist air is pumped northward from the Gulf of Mexico source region. Thus as rain rates increase Friday afternoon so will temperatures. The 'Burg and vicinity looks to remain above freezing all weekend long so there is no threat of wintry precipitation.

Snow lovers should enjoy the remaining snow cover while they can. It won’t hang around much longer and the weekend’s wetness will likely erase any and all vestiges of the white stuff.

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