Major Winter Storm Monday PM-Wednesday AM UPDATED 422 PM

UPDATE
Blizzard warnings have been posted for all Eastern MA, RI, and CT.  This includes Southern Worcester County.
NWS Hazards 1/25/15 4 PM Update
Totals have updated a bit too.  It now appears likely a large portion of Southern New England will see 2-3 feet.
NWS Boston snow total forecast
Previous discussion below.




Winter 2014-15 has started cold but rather dry.  That all changes tomorrow.  A major winter storm that may end rivaling the all time greats is on tap.  For many 1978 is the top dog and it will be hard for anything to top that storm.  For those of us who aren't AARP members or coming close this should stack up with the April Fools Day storm of 1997, the Presidents Day Storm of 2003, the Blizzard of 2005, and the Blizzard of 2013 (Nemo).   Its also a welcome distraction from deflated football talk.

Overview
The National Weather Service in Taunton has issued a myriad of watches/advisories already
NWS Boston watches and warnings
So far Worcester County/NE CT are not in the blizzard watch (lime green) but they will probably be added later today.  The official definition of a blizzard is falling/blowing snow with sustained winds (or frequent gusts) over 35 mph and visibility less than 1/4 of a mile for at least 3 hours.  The piece of energy that will become our storm is currently in Missouri/Iowa/Illinois
WPC Surface Analysis 12z (7 AM)
The high pressure in Ontario is important to note as well; it will lock in very cold air during the storm and increase the pressure gradient thus increasing wind/blizzard potential.  In terms of upper level steering
NAM 12z 500 mb vorticity 7 am (image NCEP)
Notice the potent dip in the height field traveling down the ridge in the Western US. We can see the players on the water vapor satellite loop
NOAA GOES_East Water Vapor Satellite through 1015 am
Evolution of Storm/Timing
Light snow breaks out by Monday PM say 4-5 PM.  My initial thinking was 10-12 PM but things have changed.  By 7 PM the storm will look like this
NAM 500 mb vorticity 7 PM Monday (image NCEP)
At the upper levels the Eastern trough takes on a negative tilt which will enable the storm to close off near Southern New England.  At the surface
WPC Surface Forecast Monday 7 PM
The projected radar
NAM Hi-res Simulated Radar 7 PM Monday (image Weatherbell)
Temperatures
NAM Hi-Res Temperature Snapshot 7 PM Monday (image Weatherbell)
By 7 am Tuesday we are looking at a raging Nor'Easter
NAM 500 mb Vorticity valid 7 am Tuesday (image NCEP)
The upper levels close off allowing the storm to stall out
WPC Surface Forecast 7 am Tuesday
The simulated radar
NAM Hi-Res Simulated Radar 7 am Tuesday (image Weatherbell)
With sustained winds cranking in Eastern MA, RI, coastal CT and Long Island
NAM Hi-Res 10 m winds 7 am Tuesday (image Weatherbell)
The storm will pull away Tuesday night, though the exact end time is uncertain at this point.  We have time to nail that down tomorrow.

Impacts
No need to make my own snow map- the National Weather Service is on top of this.
NWS Boston forecast Snow totals
There will likely be pockets of snow totals greater than 24 inches.  I'm thinking the Foxboro/Mansfield/Norton area as well as the North Shore.  The Cape/Islands will deal with some mixing issues keeping totals down.  Also someone will end up in the dreaded dry slot (dreaded if you love big storms).  I ended up in one during the Post Christmas Blizzard of 2010 and it sucks.  So some will end up with less than predicted, others will overachieve.

Over the Cape winds will max near Hurricane Force. In SE MA/RI winds will gust upwards of 60 mph Tuesday AM.  South of the Pike should gust to 50, everywhere else 40-45.  There is a chance of power outages.  The snow will be light as temperatures Tuesday will be in the teens.  

Multiple rounds of coastal flooding are likely as well.  Tides are not astronomically high but the storm is strong enough to cause problems.  So in summary hit the stores today and get what you need to deal with the storm.  Make sure to get some booze; there will be no travelling Tuesday!

I'll update as needed.

-Zack
















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