Wet Snow May Mix With Rain NW of DC on Monday

A wave of low pressure will skirt to our south on Monday morning producing cold rain for most and the potential for some wet snow to mix in across the outer northern and western suburbs of DC and Baltimore during the afternoon as cold air begins to infiltrate our region. The image below shows rain (green) and areas of wet snow (blue/purple). Very light accumulations are possible on grassy surfaces well north and west of the Capital Beltway.

In the Allegheny mountains several inches of snow are possible where the National Weather Service has issued Winter Storm Watches. Further east, Skyline Drive may see a dusting to two inches of snow mainly on grassy surfaces if the snow can fall heavy enough to overcome the warm ground and marginal boundary layer temperatures.

In the Washington Area, a dusting of snow is possible on grassy surfaces across the northern and western suburbs including the Bull Run and Catoctin Mountains, Leesburg, Reston, Frederick, Germantown and Gaithersburg.  The wet snow will be a conversational event only, with no issues expected on area roadways across the immediate metropolitan area (western Fairfax, Loudoun, northern Prince William and Montgomery counties).

Update on Next Week’s Potential Major Winter Storm

An area of low pressure will move out of the lower Mississippi Valley on Tuesday toward the spine of the Appalachians, meanwhile a coastal storm is forecast to develop off of the Mid-Atlantic coastline on Wednesday.    The ensemble forecast models are showing an increasing threat of a high-impact winter storm for portions of the Mid-Atlantic on Wednesday.

The image below (courtesy WxBell) shows the latest European Ensemble model and depicts quite a spread in placement of the coastal storm on Wednesday of next week. Notice some of the red “Ls” on the map below are located near Hatteras, NC while others are located just off of the Delmarva coast. The exact track will be key regarding how much cold air locks in across the populated 95 corridor from Fredericksburg to Washington and Baltimore.

Model accuracy will begin to increase once the upper level energy that will be responsible for the development of the surface lows actually makes landfall across the west coast of the United States on Monday morning.  There are not enough ocean buoys recording current weather data that the models rely upon for an accurate forecast (garbage in = garbage out). If your mathematical equation has inaccurate input data, the output, or solution will be inaccurate.

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