Latest Snowfall Forecasts from the Various Models:
Snow should break out in earnest during the morning hours in the Shenandoah Valley, pushing east into the Metropolitan Area between noon and 3PM. Snow will continue through the afternoon before beginning to mix with sleet and freezing rain during the evening hours. Freezing rain will continue overnight in the favored colder locations (Shenandoah Valley, northern Maryland) before changing over to rain. Ice accumulations will range between a tenth in our warmest suburbs (south and east of DC) to a quarter-inch or more in the sheltered valleys (Shenandoah Valley/Northern Maryland). This storm means business… and will be difficult to forecast exactly when the colder air at the lower levels is able to be scoured out. Stay Tuned.
DC Storms 
A highly unusual snow event for tomorrow, no coastal storm but just this Arctic high moving off the east coast with an intense southerly flow streaming up from the Gulf of Mexico and the south Atlantic. 99.9% of the time with this kind of set up, DC would just get rain, but with such extraordinarily cold air in place, we could get several hours of moderate to heavy snow. I am in basic agreement with your forecast map. Unlike our last storm that piddled around for hours, this storm could start much more suddenly and catch people off guard.
It appears as though Arctic air will again dominate most of the nation next week. The models seem to indicate that by the end of the month, the upper ridge along with west coast will retrograde, which could set up a potentially interesting east coast storm.