Light snow has developed in central Missouri this afternoon as a low pressure trough has dropped down from the north, dragging a pocket of cold air in its wake. Sitting over the mid Mississippi Valley, this low is pulling warm, moist air up from the south and lifting it over the cold air to its north and west. Falling through a thick blanket of subfreezing atmosphere, the precipitation is reaching the ground as snow; since the ground is relatively warm, little accumulation is expected.
Meanwhile, a stronger low is swirling over the Panhandle of Florida, bringing heavy rains to the Southeast. As this low moves to the northeast and our current storm moves to the east, the two systems will merge off the Southeast Coast. Since cold air will drop behind the Midwest low, a cold front will pass through the Mid Atlantic region just as the the storms combine, setting the stage for heavy snow from Virginia to New York.
As with all of these weather events, the track of the heavy snowfall will depend upon the relative positions of the cold front and the new, combined low. If the latter churns slowly to the northeast, paralleling the coast, significant snow will blanket the urban corridor, from Washington, D.C., to New York; if, on the other hand, it's course is more north or more east, the swath of heavy snow will shift accordingly. Either way, its going to look a lot like Christmas across the Mid Atlantic States.
