This just in, via D.C. HSEMA (emphasis LL’s):

National Weather Service has updated their Winter Storm Warning for the D.C. Metro Area, which is now in effect until 10PM tomorrow. 20-30″ of snow now expected in the D.C. area, with localized amounts exceeding 30″. Conditions will deteriorate rapidly through the afternoon today. The heaviest snowfall will be from sunset today to Sat. morning. NEAR-BLIZZARD CONDITIONS ARE EXPECTED DURING THAT TIME. Wind gusts of 20-30 mph expected by tonight, with some blowing snow. Visibilities will be appx. 1/4 mile. For your own safety, and to help your local responders, please stay off roads this evening and overnight.