An upper level trough axis should set up northwest to southeast across the Potomac river basin Monday night and into the day on Tuesday. Locations north and east of this axis will receive the steadiest snowfall Monday night and Tuesday.
Dry air will try to punch into the southern exurbs from Quantico down towards the city of Fredericksburg including areas of southern Maryland knocking down on potential snowfall accumulations.
Snow will fall the longest across northern Maryland where someone just west or north of Baltimore could potentially pick up 7″ of snow out of this. I think totals across northern Maryland will generally remain between 3 and 6″.
The immediate Washington Area (Fairfax, Alexandria, Arlington, Falls Church, Montgomery and Prince Georges county) may pick up two to four inches of snow. I can see two inches falling at National airport and the urban heat island locations with up to 4″ accumulating from Tyson’s Corner across the American Legion bridge into Potomac, Bethesda and College Park.
Temperatures will start out mild and most locations will start out as rain on Monday afternoon before transitioning over to snow Monday night and Tuesday. Snow or snow showers should taper off Tuesday evening. Temperatures will remain in the lower to middle 30s with slick travel conditions on untreated roadways.