Washington, D.C., hasn't seen more than 2 inches on the ground all season. This, then, will likely be the biggest storm of the season.
There is currently a winter storm watch for D.C., and the National Weather Service predicts 6-8 inches; over the next two days, the local NBC weather affiliate predicts about 4 inches on the ground.
A winter storm warning for heavy snow means severe winter weather conditions are expected or occurring. Significant amounts of snow are forecast that will make travel dangerous.
Snowfall rates of at least an inch per hour are possible at times Wednesday, reducing visibility to less than half of a mile. “Thundersnow” is possible.
Because of the rain snow mix and wind, The Washington Post says "power outages are possible" as well as flight delays. The nation's capital can expect a day of school closures, flight delays, and government closures. Yahoo and Best Buy may have ended telecommuting, but the federal government still has it, baby! The Weather Channel also predicts flight delays at all three D.C. metro airports.
The biggest threat with this storm, however, is downed trees, with the ABC local affiliate predicting power outages to the west of D.C., as you can see with this graphic from AccuWeather:
Philly will also see 4-6 inches of snow, and likely power outages as well.