Contest # 2 - Early Obs

The heavy snowfall over IAD / DCA / BWI earlier today was missed by all forecasters. PNS from LWX reported 2.9" at DCA with IAD and BWI each picking up 4.5". SN:H2O about 8:1 in the DC area...~10:1 at BWI.

Forecast soundings had depicted a relatively deep layer from ~1500 to 3500' AGL where the temperature was right at 0°C. 85H WAA ordinarily would have pushed the temperature trace to above freezing causing the snow to melt. Add to that the SE SFC wind with temperature at or slightly above 32°F should have spelled doom for snowfall...as well.

Strong UVM associated with the passage of the diffluent mid-level trof could have been reponsible for the dynamic cooling that keep the precipitation frozen all the way to the ground.