For the current accumulation forecast map and probabilities, check out Jason's post below.Links of InterestHere's the latest update. For history, scroll down.
9:45pm addendum:For the record, National and Dulles each reported 1" on the ground at 7pm.
Here are some more measurements around the area, including 3" at Frederickburg.
9:00pm: Mainly light snow continues throughout the Washington DC region. The southwestern edge of precipitation remains near Charlottesville, which is still reporting light snow at this hour. The rain-snow line is roughly from Richmond (currently light snow) to Ocean City (switched from snow to rain about 2 hours ago). Nearly all reporting locations in the immediate metro area are at 30°.