A Messy Solution Likely Thursday


There are two main ways to lock cold air into Southern New England before a big snowstorm.  Neither will be present on Thursday but a decent snowstorm is on the way for interior Southern New England/Northern New England.  Low pressure will track over the Canal allowing a surge of warm air to move into Eastern MA/RI/CT.  The inland track will change these regions to rain. The low will deepen rapidly as it swings into the Gulf of Maine.  Temperatures will drop sharply as this happens and a brief burst of heavy snow is likely in interior Eastern MA, South Central MA and Northern CT.  The deep pressure drop will also bring strong winds to Southeastern New England.

General Overview
If you notice the Thursday 7 PM surface chart in the headline graphic above note there is no high pressure in Southern Canada.  It is neither present in banana form (or Midwest Extension) as it was on December 26, 2010
WPC Surface Analysis December 26, 2010 7 PM
Nor is it present on its own as it was on January 27, 2015 in my personal favorite blizzard.
WPC Surface Analysis January 27, 2015 1 AM
The high is important to lock cold air into Southern New England.  It is also important that the low pressure center track offshore of Nantucket near the 40/70 benchmark.  With no cold air to lock in and a low track over Southeastern MA the big ingredients for a big snow are missing from the atmospheric recipe.

On Thursday AM the initially weak surface low makes it way towards the Mid Atlantic coast.  High pressure is in the picture for the time being but it will continue to move east on Thursday.
WPC Surface Fronts/Precipitation Thursday 7 AM
Thursday Outlook
A mix of snow and rain will move into Southern New England Thursday between 10AM- Noon.  Expect steady snow in Southern NH, VT, and Western MA by this time.  Rain will be steady in Southwestern CT and on the move east.
18z NAM hires simulated radar Thursday 1 PM (image Weatherbell)
At 4 PM
18z NAM hires simulated radar Thursday 4 PM (image Weatherbell)
7 PM
18z NAM hires simulated radar Thursday 7 PM (image Weatherbell)
At this point the rain snow line will be messy.  Given the strength of the low crossing the region and temperatures in the low to mid 30's intense precipitation may change over to snow.  That is what I will be watching over the next 48 hours.  A *Winter Weather Watch* has been posted but rain and wind is likely to be the main players South of the Pike and inside 495.  I expect Southern Worcester and Northern Middlesex to be placed under Winter Weather Advisories for this event.  The rest of interior will post Winter Storm Warnings.
NWS Headlines Tuesday December 27, 2016
I'll post another update tomorrow night with precipitation amounts and wind forecasts.  Here is the NWS snow map
NWS Most Likely Snowfall 
-Zack Green


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