UPDATE VI: Current AccuWeather Radar for the Middle Atlantic States here. The map above depicts 15" snow forecasts in red with the redish-gray within a forecast of more than 18". Note this extends into New York-Hartford and almost to Boston.
UPDATE VII: From the National Weather Service:
...RECORD BREAKING DECEMBER SNOWFALL FOR BALTIMORE-WASHINGTON METROPOLITAN AREAS BRINGING HAZARDOUS WINTER WEATHER TO THE REGION OVERNIGHT AND SATURDAY... TOTAL STORM SNOWFALL TOTALS OF 1 TO 2 FEET ARE FORECAST TO OCCUR IN THE BALTIMORE-WASHINGTON METROPOLITAN AREAS BY DAWN SUNDAY...WHICH SHOULD ECLIPSE THE DECEMBER RECORDS FOR BOTH CITIES. THE RECORD DECEMBER SNOWFALL FOR WASHINGTON IS 12.0 INCHES ON 18-19 DECEMBER 1932...AND FOR BALTIMORE TO RECORD IS 14.1 INCHES ON 12-13 DECEMBER 1960
Most all flights to Washington, Baltimore and Richmond are already cancelled for Saturday. AccuWeather's Flight Delay tools are here. Use your airline's website to check for flight irregularies before you head to the airport Saturday as this storm will cause problems outside the Middle Atlantic States.
Finally, flooding is an increasing problem in southeast Louisiana, southern Mississippi and Alabama, and the Florida Panhandle.