The various models (ECMWF, GFS, Canadian) continue to portray different evolutions of a complex, double-barrel storm system forming over the East. All models develop heavy snow within the Mid Atlantic as the primary low over the Tennessee Valley transfers its energy to a coastal low Sunday night. A shallow layer of cold air will remain wedged in between the systems, dammed up against the Appalachians.
However, the trends and consensus among the models support the notion that the D.C.-Baltimore region will NOT be in the heavy snow bulls eye; that will unfold over the higher elevations either to our west, or to our north and west. Warm enough air will invade on east winds off the Atlantic to prevent an all-out heavy snow storm. What appears to be on tap for here is a 12-18 hour period of "wintry mix" meaning rain, sleet, and wet snow.
Here are two of today's model runs, and their snow accumulation predictions:
Here is the Canadian model's forecast snow accumulation:
The NOAA Weather Prediction Center states that the chance of a major D.C. - Baltimore - Philadelphia snow storm is 10%.
Again, there is a complex storm evolution involved here, so future refinements to this scenario are probable.