The image above shows the latest HRRR (High Resolution Rapid Refresh) model showing the future-cast radar through 9AM Tuesday.
Some of the mountain snow that occurred may rotate back southeastward into Washington’s northwestern suburbs.
Temperatures are likely too warm for anything more than a slushy dusting on grassy surfaces but some of the higher elevations along the Blue Ridge could see some slick spots as temperatures drop into the lower 30s.
The image above shows a closer look at the immediate Washington Metro Area.
If this model is accurate, some wet snow may being falling across Loudoun and Frederick county and yes its even possible some wet snow flakes may make it into northwestern Fairfax and upper Montgomery county before or around midnight.
DC Storms 
I recently talked to one of my workers, who said that I-81 was icy and slippery between Winchester and Hagerstown due to mixed sleet and snow. Traffic was moving terribly.