Severe Weather Likely Tomorrow

Powerful thunderstorms have left a swath of damage across the Upper Midwest and Great Lakes today.  Tomorrow this system will slide east and bring the severe weather threat to New England.  Everything is on the table including tornadoes.  That said all the ingredients need to come together for widespread severe weather outbreak. 

A large complex of showers and thunderstorms is speeding through the Great Lakes.  This complex has a history of producing wind gusts over 74 MPH.
NWS Great Lakes regional radar 238 EDT
Here are the storm reports so far
SPC Storm reports for Monday (as of 341 PM)
At the surface we see a wave of low pressure and an accompanying warm front forcing its way through Michigan.
WPC surface analysis 2 PM
This is being driven by a potent shortwave in the middle levels of the atmosphere.  It is sliding above a mid level ridge in the southwest
12z NAM 500 mb vort, heights 2 PM Mon (image NCEP)
By tomorrow afternoon the upper air pattern will evolve into this
12z NAM 500 mb vort, height 2 PM Tues (image NCEP)
The surface chart will look like this
WPC projected surface chart Tuesday 2 PM
This puts NH, VT, western ME, and all of Southern New England in the warm sector.  The orientation of the upper air will allow for a surge of low level moisture into the region.  Remember thunderstorms need a trigger, a source of low level moisture, and an unstable atmosphere.  We have the trigger (the cold front) and the low level moisture.  High resolution guidance is indicating dew points in the low 70's tomorrow afternoon
12z NAM hi-res 2 m dew points  Tuesday 5 PM (image Weatherbell)
 High temperatures at the same time will surge into the upper 80's.  So all we need to do is have some cooling in the middle layers of the atmosphere to make it unstable and allow for the cumulus clouds to tower high up into the atmosphere.   Clear skies tomorrow morning/early afternoon will be an indication of whether or not we see a big time severe weather event or just some isolated severe thunderstorms.  The SPC has areas north of the Pike, west of 495/395 in an enhanced severe weather risk meaning scattered to widely scattered severe thunderstorms capable of large hail, damaging wind, and isolated tornadoes is likely.
SPC Tuesday severe weather outlook
That's really all for now.  We (meteorologists) need to see what the atmosphere and radar look like tomorrow morning to know for sure.  What we do know is that a significant event is possible.  Stay weather alert tomorrow.

I'll have an update as early as possible tomorrow AM.

-Zack Green


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