Granted, it won’t be a lot of snow… mostly just a quick shower for the MD/DC region along a cold front that will push through the region tonight. To the north and west, the snow is expected to be a bit more robust as a quick thump of snow along a squall line of sorts (which could be thundersnow in PA as the lapse rates allow for conditional instability) could lead to accumulations of around one inch in the upslope areas of western/central PA down through the MD panhandle into east-central WV.
The strength of the snow squall varies on the models… here is a look at one of the more potent outcomes via the HRRR composite reflectivity around mid-evening:
And this is how it looks a couple hours later as it approaches the DC region… note that it has weakened a fair amount by this point:
East of the mountains could see a quick dusting to an inch of snow from this line of snow as it pushes through the region. This is much more likely in the northern Mid-Atlantic (PA down through around DC) than it will be in the southern areas as the upper-level energy driving this snow squall slides eastward across PA:
You don’t get a snow squall along a cold front in the Mid-Atlantic that often as temperatures are typically too warm ahead of the cold front, but this time the low-level temperatures should be cool enough to allow for snow, especially the further north you go.