(Update- 11:20 a.m.: To clarify my comment above – I think the 5″+ assessment is aggressive, not because it’s impossible, but because it’s a “boom” (high-end) scenario – rather than the most likely scenario. Having said that, I don’t want to be overly critical of NWS as the storm will be coming in around rush hour and could have a high impact. It’s a borderline Winter Storm Watch situation, overall.)
In the mean time, here’s the National Weather Service’s watch statement, in full:
1009 AM EST MON DEC 9 2013 ...WINTER STORM WATCH IN EFFECT FROM LATE TONIGHT THROUGH TUESDAY AFTERNOON... THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS ISSUED A WINTER STORM WATCH...WHICH IS IN EFFECT FROM LATE TONIGHT THROUGH TUESDAY AFTERNOON. * PRECIPITATION TYPE...POTENTIAL FOR HEAVY SNOW. THE PRECIPITATION MAY START AS A PERIOD OF SLEET...ESPECIALLY SOUTH OF INTERSTATE 66 IN VIRGINIA...THE DISTRICT OF COLUMBIA...AND U.S. ROUTE 50 IN MARYLAND. * ACCUMULATIONS...POTENTIAL FOR FIVE INCHES OR MORE OF SNOW. * TIMING...NEAR DAWN TUESDAY THROUGH EARLY TUESDAY AFTERNOON...INCLUDING THE TUESDAY MORNING RUSH HOUR. * TEMPERATURES...UPPER 20S AND LOWER 30S. * WINDS...NORTH 5 TO 10 MPH. * IMPACTS...HAZARDOUS TRAVEL CONDITIONS ARE PROBABLE DUE TO ACCUMULATING SNOW...WHICH WILL CAUSE ADVERSE TRAVELING CONDITIONS. THE SNOW WILL LIKELY IMPACT THE MORNING RUSH TUESDAY WITH THE POTENTIAL FOR ACCUMULATION RATES OF 1-2 INCHES PER HOUR FOR A TWO-TO-FOUR HOUR PERIOD FROM DAYBREAK TO MID-TO-LATE MORNING. PRECAUTIONARY/PREPAREDNESS ACTIONS... A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL. CONTINUE TO MONITOR THE LATEST FORECASTS.
Here’s the National Weather Service’s snowfall map – from its office in Sterling, Va.:
Interestingly, the NWS office in College Park suggests amounts over 4″ are a fairly low probability – just a 20-40 percent chance: