High-Impact Snowstorm Headed For Mid-Atlantic

The Mid-Atlantic states are bracing for a high-impact, heavy snowstorm starting late Tuesday and lasting through Wednesday. The storm has the potential to paste parts of Virginia and Maryland with more than a foot of snow, while ending Washington, D.C.’s longest snow drought on record. The nation’s capital hasn’t received two inches or more of snow in a single event since Jan. 26, 2011, the longest such stretch since weather records began there in the late 1800s. 

Simulated radar from the NAM computer model, for Wednesday afternoon.
Click on the image to enlarge it. Credit: WeatherBell.com.

The prospect of heavy, wet snow along with high winds means that this storm poses a significant risk of power outages in a region that experienced lengthy power disruptions following severe thunderstorms last summer and Hurricane Sandy last fall.

The storm also threatens to cause coastal flooding from Virginia northward, possibly all the way to Massachusetts. The National Weather Service office in Philadelphia warned of the potential for “major coastal flooding” to take place along the vulnerable New Jersey shoreline, which was severely damaged during Sandy in October 2012. Fortunately, astronomical tides are not running particularly high, which should limit the flooding potential.

Computer models have been giving forecasters fits when it comes to predicting the exact snowfall amounts, but confidence is high that a major storm will strike the Mid-Atlantic region. Model updates from Monday afternoon indicated an increasing possibility that the storm will affect a broader swath of the East Coast, possibly reaching up as far as Boston.

Temperatures at the surface are going to be marginal for snow in the Washington and Baltimore metro areas, but if the precipitation falls heavily enough, as many projections indicate it will, then colder air aloft will be dragged to the surface, and snow would accumulate even if surface temperatures are in the mid 30s.

As of Monday afternoon it looked like Philadelphia and New York City would be on the northern edge of the precipitation shield and would be spared a big snowstorm, but there are more questions about how the storm will affect southern New England. One of the main computer models used for forecasting the weather, known as the Global Forecast System (GFS), has been showing that the storm will move farther northward and park itself near Cape Cod, lashing southeastern New England with wind-whipped rain and snow.

The Washington Post’s Capital Weather Gang blog has nicknamed the storm “snowquester,” since it comes in the first week of the automatic federal budget cuts known as the “sequester.” The Weather Gang's forecasters are predicting that the heaviest snow will pile up well west of D.C., especially at higher elevations in Virginia. (Meanwhile, the Weather Channel has named the storm “Saturn”, setting up a naming duel for the largest share of the social media conversation in the Mid-Atlantic.) Still, D.C. itself could see between 3 to 8 inches of snow, and possibly more, depending on the exact track and strength of the storm, according to the blog's forecast and National Weather Service data.

The storm is expected to draw in copious amounts of moisture from both the Gulf of Mexico and the Atlantic Ocean. Indications are that at least 2 inches of liquid precipitation could fall somewhere in the Mid-Atlantic during this event. That could translate into nearly two feet of snow depending on air and surface temperatures.

Heavy snowstorms are entirely consistent with climate change projections. Scientists expect that major snowstorms will continue to occur as the climate warms, in part because warmer air and ocean temperatures will increase the amount of water vapor in the atmosphere. That added water vapor could fuel unusually heavy snowstorms, such as the blizzard that buried parts of New England under 40 inches of snow in early February.

Recent observations do show more frequent heavy precipitation falling in many areas, although it has not been the case in every region and season.

A forthcoming paper in the Bulletin of the American Meteorological Society found there were more than twice the number of extreme regional snowstorms from 1961-2010 in the U.S. as there were in the previous 60 years.

“The greater number of extreme storms in recent decades is consistent with other findings of recent increases in heavier and more widespread snowstorms,” the study said.    

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