Connecticut and most of Massachusetts are under a Severe Thunderstorm Watch until 10 pm Thursday evening. An approaching cold front will combine with warm, humid air over the Northeast to trigger widespread thunderstorms Thursday afternoon and night.
The best chance of seeing severe thunderstorms is away from the coast, and the Storm Prediction Center has left RI and SE MA out of the Severe Thunderstorm Watch. Thunderstorms are still possible in RI and SE MA, but there is a lower chance that they will produce damaging winds and flooding rain. Scattered thunderstorms are popping up in interior Southern New England Thursday afternoon. An organized line of thunderstorms is likely to move through SNE Thursday night.
The following is a technical discussion from the Storm Prediction Center that discusses the scientific reasoning behind the issuance of the Severe Thunderstorm Watch.
MESOSCALE DISCUSSION 1878 NWS STORM PREDICTION CENTER NORMAN OK 1124 AM CDT THU SEP 12 2013 AREAS AFFECTED...NEW ENGLAND CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 121624Z - 121730Z PROBABILITY OF WATCH ISSUANCE...60 PERCENT SUMMARY...SEVERE THUNDERSTORM WATCH MAY BE REQUIRED SOON TO ACCOUNT FOR ONGOING CONVECTION AND NEW DEVELOPMENT LATER THIS AFTERNOON. DISCUSSION...SFC TEMPERATURES ARE WARMING THROUGH THE 70S INTO THE LOWER 80S ACROSS MUCH OF SRN NEW ENGLAND EARLY THIS AFTERNOON AND RESULTANT INSTABILITY HAS INCREASED SUBSTANTIALLY ACROSS CT/MA/SERN NH. CONVECTION IS RESPONDING ACCORDINGLY WITH ROBUST UPDRAFTS INCREASING IN INTENSITY/COVERAGE ALONG A CORRIDOR FROM THE LOWER HUDSON RIVER VALLEY...NEWD INTO EXTREME SRN ME. THIS TREND IS EXPECTED TO CONTINUE INTO THE MID AFTERNOON HOURS AND GIVEN THE VERY MOIST AIRMASS...PW VALUES ON THE ORDER OF 1.75-2 INCHES...DAMAGING DOWNBURSTS MAY ACCOMPANY THE STRONGEST CONVECTION. NWD EXTENT OF SEVERE THREAT WILL BE LIMITED BY EXTENSIVE CLOUDINESS/MORE STABLE CONDITIONS OVER NRN ME.