A shot of cool air is expected this weekend up and down the eastern U.S., with lows in the 30s possible in the higher elevations and maybe even northern MD. DC looks like it will stay in the low to mid 40s at its coldest point on Sunday morning (and possibly Monday morning).
The 12z GFS is pretty aggressive with the cold, showing widespread 30s and even some 20s in the region Monday morning (similar to Sunday morning, only the 30s reach further east Monday morning as high pressure moves overhead):
On top of the cooler temperatures, some snow showers could develop Saturday morning in the higher elevations, with a flurry or two possible Sunday morning up in the mountains. Some minor accumulation is possible in the highest areas, otherwise the snow that does fall should not accumulate. I wouldn’t rule out seeing a flake or two in the air in northern VA/MD, but it looks unlikely at this point.