Afternoon Heavy Rain/Thunder Threat

A stalled backdoor cold front will focus shower and thunderstorms across Eastern Southern New England this afternoon.  Areas to the west of the front are near 90 with excessive dew points.  Areas east are in the 70's.  The clash of air masses will lead to some interesting weather.  Currently the radar is quiet.  My feeling is it won't stay that way for long.

General Overview

Let's play a game of find the cold front.  

1208 PM Wunderground temperatures

If you guessed right through Worcester County you are correct

WPC Surface Analysis 8 AM 

Here are the dew points

NCEP 2 M dew points 11 AM 

As a result heat advisories and excessive heat warnings have been posted in Western MA, CT, RI and Southern Worcester County.

NWS Headlines/Hazards 12 PM

Being at the boundary is problematic for several reasons.  A few miles is the difference between 15-20 degrees and 5-10 in dew points.  Convection will also focuses at and just west of the boundary.  Given the available moisture in the atmosphere several of these storms could sit over the same area and dump a lot of rain.  Flash floods are possible in NW MA into N CT, N RI and CMass.   Here is the simulated radar for 3 PM

15z HRRR Simulated Radar 3 PM (image Weatherbell)

Storms won't be in these exact locations but the message is eyes to the sky after 2 PM.  Convection is firing to our west in Upstate NY already.  Any of these cells needs to be watched carefully near the front.  There is a natural change in wind direction at the boundary.  Set ups like this have been known to spin up brief tornadoes such as the one in Worcester Labor Day weekend 2014.  

5 PM

15z HRRR Simulated Radar 5 PM (image Weatherbell)

I'll be on the radar.  Similar weather tomorrow except the front will push back north and east returning the whole region to hot/humid.

-Zack Green