An energetic weather disturbance promises to deliver the Washington, D.C. metro region one more round of snow Tuesday.  An inch or so of snow is certainly possible, especially in our colder suburbs.  But what will be an ordinary storm for us will transform into an absolutely monstrous cyclone over the ocean waters east of New England.

What to expect around Washington, D.C. Tuesday:

* Light snow may develop just before dawn Tuesday. Periods of snow are likely during the day Tuesday, especially in the morning.  Coverage likely diminishes in the afternoon, but scattered snow showers remain possible into the evening, especially east of the city.

GFS model forecasts snow over the region Tuesday morning into the early afternoon (

* Temperatures early-to-mid morning Tuesday should be near freezing in the city and below freezing in the suburbs, so some light accumulations are possible, especially on grassy areas – and even a little on the roads.  During the late morning and afternoon hours, temperatures should rise above freezing, into the mid-to-upper 30s, so lingering snow showers probably won’t accumulate much.

* Accumulation potential is generally around 1″ or so.  The high-end of possible accumulations would be in 2-3″ range (based on current information.)

* Chance of at least 1″: I-95 corridor and points east, 30-40 percent. Manassas to Fairfax to Rockville to Columbia, 40-50 percent. Leesburg to Frederick, 50-60 percent.

From CWG’s winter weather expert, Wes Junker: “The good news is that the storm is forecast to develop far enough offshore to keep any heavy precipitation well to our east. However, the pesky upper level system has a favorable track to bring some snow to the region albeit probably on the light side.  The timing of onset has shifted just enough to give the system the potential to give the area light accumulations, maybe a slushy inch or so early Tuesday morning before it warms above freezing.  The best chances for an inch will be the colder northern and western locations.”

The oceanic beast

I am in total awe of the simulations for this storm’s intensification after it gives our region a little bit of snow (we will, for sure, miss the brunt of it).

At 2 p.m. Tuesday, the European model forecasts the storm to have a central pressure – off the coast of the Carolinas – of around 1,002 millibars (mb) – which is nothing special.  But by 2 p.m. Wednesday, when the storm moves to a position offshore New England , the pressure nose dives  to a jaw-dropping 946 mb.  This pressure is equivalent to what’s inside a category 3 hurricane.

European model simulation of explosive development of storm between 2 p.m. Tuesday and 2 p.m. Wednesday (


The rate of intensification – indicated by the 56 mb pressure fall in the 24 hours – is simply phenomenal.  Bear in mind, a storm is considered a meteorological “bomb” if its pressure drops 24 mb in 24 hours.  This storm is forecast to have its pressure decrease at more than double that rate.

Fortunately, the storm explodes far enough offshore that the Mid-Atlantic is largely spared. Even New York City and Boston probably are only dealt a glancing blow although a slight shift west could bring heavy snows and wind (over 40 mph) to Boston.  The very easternmost parts of New England, including Nantucket and Cape Cod, are likely to get heavy snows and 50-60 mph winds from this storm. A shift in the storm track to the west could bring hurricane force wind gusts to this area while a shift east would bring more modest 30-50 mph winds.

The National Weather Service Forecast office in Boston has a good discussion which walks through the different scenarios for the Boston area and the Cape.

We will have additional updates tomorrow.