Monday, November 24, 2014

Winter Storm Watches Posted for Wednesday

A coastal storm will bring accumulating snow Southern New England Wednesday into Wednesday night/early Thursday morning.  Without any true Arctic air locked in there will be a fine line between rain/snow.  As it stand now this line should work back towards 495, but will struggle to get much further.  The Cape, Southern RI, and Coastal CT will likely be shut out.

NWS Boston Headlines
General Overview
Low pressure forms in the Gulf of Mexico tomorrow afternoon
WPC 1 PM surface forecast Tuesday
By Wednesday AM the system will begin to deepen off the North Carolina coast.  This storm will not "bomb" on its way up the coast nor will it phase with another low diving through the Midwest; the pattern is moving too fast.  
WPC 7 am surface forecast Wednesday
There is some relatively warm water off the East Coast so that will enable some strengthening 
OSPO NOAA Sea Surface Temperatures (C)
More importantly this system will develop in the Gulf meaning it will bring lots of tropical moisture with it.  Here are the 3 day precipitation totals, ending Thanksgiving night at 7 PM
WPC 3 day precipitation forecast, valid through Thursday 7 PM
Timing and Impacts
Precipitation will begin after the Morning Rush, but before lunchtime on Wednesday.  Temperature profiles are not ideal as mid level temperatures are initially warm.  This means many places begin as rain, but the colder spots will begin as the dreaded freezing rain.  As the intensity of the precipitation increases interior locations will flip to snow.  This looks to happen shortly after noontime.

Around 4-5 PM, as the sun sets, the snow should really begin to stick.  The heaviest is Wednesday PM.  So how much snow
Guidance is suggesting a possibility of more snow.  I may bring totals up closer to 495/95; it will depend on the temperatures.  

On Thanksgiving morning this should be pulling away.  The football games will be interesting on Thursday morning.  Temperatures will be in the low 30's with 15-25 mph wind gusts.  

12 years ago 6-10 inches of snow fell the day before Thanksgiving cancelling school for the day
NWS Boston snowfall map 11/27/2002
We also woke up to snow Thanksgiving morning 2005, though not as much and it warmed up nicely that day.
NWS Boston 11/24/2005 snowfall map
Its also been 65 (2003, 2007, 2009) or pouring with rain (2004, 2006).  

Questions? twitter @zgreenwx .

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