Current Conditions:
Temperatures are currently hovering in the mid to upper 30s across most of the region, with Reagan National as the warm spot at 41 degrees last hour. Temperatures are expected to fall into the low to mid 20s overnight as clouds thicken from the south and west, as a large developing surface low moves northeastward.

The snowfall forecast for tomorrow is a tricky one, since surface temperatures, once again, will be very marginal for accumulations.

Winter Storm Breakdown:
Snow should begin to fall by 12PM or so in the District, earlier to the southwest, and later to the north and east. The surface temperature profile will be critical to this forecast. At this point, our best estimate is that the snow will change to sleet and then rain by 4-6PM as warm air filters in from the east.

By the time the precipitation change-over occurs, however, there is the potential for a Trace to 2 inches of snow in and around the District, and 1-3 inches out to the north and west of town, where temperatures will likely remain colder.

If temperatures fall just a few degrees below forecast levels, a significant change to snowfall totals would be needed. At this point, however, I am not convinced areas in and around the District stay below 32 for very long after 4 or 5PM.

Snowfall Forecast:
I think most locations, even out towards Martinsburg, WV and Harisonburg, VA will change over to rain, it will just take longer, thus the higher snowfall totals out that way. There will likely also be a period of freezing rain in the lower portions of the Shenandoah and out towards Garret County, MD. I anticipate a light glaze of ice around the aforementioned areas.