Winter Storm Update

Water Vapor shows upper low and jet stream...click to enlarge

Surface low tracking east on frontal boundary...click to enlarge

RPM snow forecast...click to enlarge

The first significant snowfall in almost a month continues to move into central Maryland this evening.  Compared to last year’s record-breaking February snowfall, the second month of 2011 has been downright balmy.  Only a trace of snow has been measured so far this month at BWI-Marshall (last February 50″ of snow was measured there), and the average temperature of 37.7F is 3.2 degrees warmer than normal, and a whopping 6.8 degrees warmer than February 2010.

However, a more familiar February weather pattern is unfolding tonight.  Water vapor satellite imagery shows an upper level low pressure system over the upper midwest and a strong jet stream zipping from Baja California into the Ohio valley and mid Atlantic states.  The jet separates bitterly cold, arctic air over New England, from warm, Spring-like air over the southeastern U.S.  Low pressure near the surface has formed on that boundary and  is moving east toward Virginia tonight.  As the low passes south of the region, the cold air over New England should be drawn south into the storm, changing a rain/sleet mix to a period of moderate to heavy snow.  The upper jet stream is carrying the system east/northeast very quickly and the snow should taper off by dawn.

Current indications are that 4-8″ of snow will fall over much of Maryland north of a D.C. to Annapolis to Centreville line.  Some areas near and just north of the Pennsylvania line could receive a little more than 8″.

Tom Tasselmyer

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