The trigger for the possible snow is a strong upper level disturbance that will ride along the jet stream carving a deep trough through the eastern U.S. into which the cold air will spill.

Precipitation may break out very late Friday night or very early Saturday morning – probably starting as rain. The precipitation could mix with or change to snow towards dawn Saturday as the air gets a bit colder.

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Whether we have a period of steady rain and/or snow or just widely scattered showers depends on the exact track of the disturbance which is difficult to pin down this far out.

The GFS model, shown below, simulates some snow falling Saturday morning, as does the European model, not shown.

The best chance of snow accumulation will be in the higher terrain of West Virginia and western Maryland, where several inches can’t be ruled out above 2,000 feet, as shown in the GFS model forecast map below.

Although we can’t rule out some slushy snow in grassy areas in northern Maryland and even in some of our colder north and west suburbs (upper Montgomery and Loudoun counties), the snow accumulation shown at lower elevations in the above map is probably overdone. The map doesn’t sufficiently take into account above freezing ground and air temperatures.

The European model shows temperatures too warm to support accumulation at low elevations Saturday morning:

But the GFS model has temperatures near freezing just north and west of the District, which would open the door for snow to whiten grassy areas in our colder areas:

I think an average of the two model represents the most likely temperatures early Saturday – in the mid-to-upper 30s.

By mid-to-late afternoon on Saturday, precipitation should rapidly pull off east of the metro region.

Temperatures tank Saturday night once the disturbance passes by with widespread freezing low temperatures.