Winter Storm to Impact Southern New England

The National Weather Service in Taunton has issued Winter Storm Warnings for all of Southeastern New England and Blizzard Watches for the Cape, Islands, and Southern Plymouth County.
NWS Boston Advisories 
Low pressure will develop along a polar front and intensify south of New England.  This will bring heavy snow and high winds to Southeast New England

The Set-Up
An approaching Polar Front will cause temperatures to plummet tonight.  The front is approaching Worcester now (449 PM).  It shows up nice on radar
NWS Boston Radar 438 PM
Here is the front in the surface analysis as of 1 PM.  
WPC Surface Analysis Northeast US 1 PM 
Here are the temperatures behind the front
2 m temps 4 PM (image Weatherbell)
This cold will be locked in place so there no precipitation type issues.  Now lets take a look at how this system will evolve.  Here is the current Water Vapor Loop
NOAA GOES_East Water Vapor Satellite (415 PM)
Low pressure will develop in the Tennessee Valley this evening/overnight.  Here is the upper level at 1 am Tuesday
18z NAM 500 mb vort/heights 1 am Tues (image NCEP)
A surface low will have developed in Eastern Kentucky and Tennessee
WPC Surface Forecast 1 am Tuesday
By 7 PM tomorrow night the upper level looks like this
18z NAM 500 mb vort/heights Tues 7 PM (image NCEP)
That is an exciting 500 mb set up for weather weenies everywhere.  Here is the projected surface chart at the same time
WPC Surface Forecast 7 PM Tues
Short Term Forecast
After the snow squall this evening temperatures will steadily drop.  The high temperature for Tuesday may occur at Midnight in some locations.  Temps are around 10 around 7 am for many in the interior.  Temps in the coastal plain will be between 15-20 
18z NAM hires 2 m temps 7 am (image weatherbell)
The temps do not rise much tomorrow.  The Cape and Islands stay in the 20s and will rise to near 30 during the storm.  Everyone else is 15-20.  Winds will be out of the north at 5-10 mph.  

Timing
The first light flakes start falling around noon time but steady snow arrives to the CT coast around 1-2 PM.  This spreads to SE RI and MA by 3-4 PM.  The precipitation will build into Central and Eastern MA by 6-7 PM.  Snow lasts until 6-7 am for everyone except Eastern MA.  In Eastern MA snowfall will stop by 10 am, with the exception of the Outer Cape.

Winds
The strongest winds will occur where the Blizzard Watches are posted.  On the Cape and Islands will will be sustained 25-30 mph with gusts to 50.  Nantucket and the Outer Cape will likely see isolated gusts to 60 mph.  Inland winds will be sustained 15-20 mph with gusts to 40, isolated 45-50.

Snowfall
Now for what you have all been waiting for.  First of all here are my observations on the storm.
  • Very cold, so a powdery snow like the 1/2/14 event
  • Storm will track South and East of "benchmark" so heaviest precipitation remains offshore
  • SE MA, Cape Ann the likely Jackpot areas
  • Tougher call inland due to precipitation rates
I have little doubt this will be a memorable storm for SE MA.  Its not often the Cape and Islands get a storm that is all snow.  I think ocean enhancement north of Boston will set up a jackpot band there as well.  A lesson learned on 1/2/14 was that the cold doesn't always mean high snow ratio's.  In general weathercasters assume for every 1" of liquid precip that is 10" of snow.  When it gets colder snow can fall at ratios of 20 or even 30/1.  We saw this in Eastern MA on 1/2.  However inland the snow growth zone was not as good so even though there was about 0.6 inches of precip, only about 6-8 inches of snow fell.  

Issued 606 PM 01/20/14
I'm going to try and post a video tonight or tomorrow morning.  Take care, feel free to ask questions.

-Zack Green



















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