Cold air stuck at the surface is being quite stubborn in giving way to a blob of warm air that wants to move in. Warm air will eventually win this war, but how quickly it does so remains a question. Otherwise, we are stuck with the low cloud cover for the duration tonight, with some patchy fog likely to develop in low-lying spots. Low clouds and cool air will be stuck at the surface in the morning. Warm air should eventually win the battle and flood the area sometime in the afternoon, though the timing on this is uncertain.

Source: Washington Post February 19, 2018 22:23 UTC