Wednesday, March 29, 2017

Large Storm System Headed Towards SNE Fri-Sat

A large storm system will move south of New England Friday-Saturday bringing a plethora of precipitation types.  Some will see heavy rain, some will see heavy snow, some will see freezing rain, and some will see all of the above.  This is a traditional early spring nor'easter that will feature lots of precipitation, marginal temperatures, and a strengthening low to our south.   Let's time the storm out and discuss when the various p-types could impact your backyard.

General Overview
Over 1" of rain has fallen in the last 3 days across parts of Southern New England.
NWS 72-hour precipitation analysis (image Weatherbell)
This is a good thing for our drought situation because the ground is able to effectively absorb moisture this time of year.   There might be a few showers on the Cape today but the region is generally dry until Friday.  Temperatures this afternoon will max around 50 as a developing NW wind dries out the lower atmosphere.  The sky will be mostly gray with only a few breaks of sun.  The clouds will break tonight and temperatures will fall into the mid 20's by daybreak.
NWS Min Temps Thursday AM (image Weatherbell)
Here is the current water vapor satellite.  Our next storm system is in the central US.  Unfortunately, this storm system produced severe weather yesterday and several storm chasers died in a car accident while trying to catch up to a reported tornado on the ground.   It's a sad day for the weather community, especially the storm chasing community.  More severe weather is likely in the Southern Mississippi Valley and parts of the Plains.
NOAA/NWS/NCEP GOES Water Vapor Satellite through 915 AM
By tomorrow at 8 AM, the storm will be
WPC Surface Fronts/Precipitation Thursday 8 AM 
High pressure will be in control tomorrow so skies will be mostly sunny with max temperatures around 50.  So far this week temperatures have trended colder than forecast but with the sunshine tomorrow and winds out of the northwest at 5-10 MPH the upper 40's/low 50's seems reasonable.
NWS Max temp Thursday PM (image Weatherbell)
Low temperatures Friday AM are expected to be right around 32, right when the precipitation begins.

Friday-Saturday
Parts of Western MA/CT will see snow begin around daybreak.  The intensity of the snow will determine its ability to stick to the roads.  This band of precipitation will move into Central/Eastern Southern New England after 8 AM.  South of the Pike this will quickly go over to a mix of sleet, freezing rain, rain, and snow.  Spring snow is generally heavy and wet so that is a concern, but of greater concern is the threat of freezing rain.
12z NAM hires sim radar Friday 8 PM (image Weatherbell)
As of 8 PM Friday night I think all of New England north of the Pike will see some sort of frozen precipitation.   The low will be re-developing south of New England at this time.  The wind will shift to the east so SE MA/RI/E CT will warm well above freezing.  The precipitation will exit by late Saturday AM/early PM.
WPC Surface Fronts Saturday 8 AM
The low will be large, but not very strong.  Still, winds will gust 30-50 MPH in SE MA.  There may be some coastal concerns thanks to the long duration and large fetch.  Beach erosion and minor coastal flooding are possible.  So in general, this is what I expect.

For Southern New England, I am not expecting major snow totals.  It's not impossible (more on that later) nor unprecedented but I think that is more likely for Central New England.  I am much more concerned about the potential for damaging freezing rain in Worcester County and the Berkshires.  Long for an update tomorrow AM.

-Zack Green



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