URGENT - IMMEDIATE BROADCAST REQUESTED
   SEVERE THUNDERSTORM WATCH NUMBER 489
   NWS STORM PREDICTION CENTER NORMAN OK
   335 PM EDT THU JUL 5 2007
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   SEVERE THUNDERSTORM WATCH FOR PORTIONS OF 
   
          MUCH OF CONNECTICUT
          MOST OF MASSACHUSETTS
          SOUTHWEST MAINE
          SOUTHERN AND CENTRAL NEW HAMPSHIRE
          EASTERN AND SOUTHEASTERN NEW YORK
          NORTHERN RHODE ISLAND
          SOUTHERN VERMONT
   
   EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 335 PM UNTIL
   900 PM EDT.
   
   HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
   MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
   
   THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70
   STATUTE MILES NORTH AND SOUTH OF A LINE FROM 35 MILES NORTH OF
   MONTICELLO NEW YORK TO 25 MILES EAST NORTHEAST OF PORTSMOUTH NEW
   HAMPSHIRE.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
   ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).
   
   REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
   FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
   AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
   THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
   AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
   DO PRODUCE TORNADOES.
   
   OTHER WATCH INFORMATION...CONTINUE...WW 487...WW 488...
   
   DISCUSSION...TSTMS/POSSIBLE SUPERCELLS EXPECTED TO INCREASE IN
   COVERAGE AND INTENSITY THIS AFTN IN ZONE OF 30-40 KT DEEP WLY SHEAR
   AND SFC HEATING FROM THE LWR MOHAWK AND LWR HUDSON VLYS ENE INTO
   CNTRL/SRN NEW ENGLAND.  LOCALLY-BACKED FLOW INVOF THE HUDSON AND CT
   RVR VLYS MAY ENHANCE POTENTIAL FOR LOW LVL STORM ROTATION AND
   ISOLATED TORNADOES...BUT MAIN SVR THREATS SHOULD BE DAMAGING WINDS
   AND HAIL FROM SCTD SUSTAINED SUPERCELLS AND/OR SMALL BOWS IN
   MULTICELL BANDS.
   
   AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
   TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
   KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
   MOTION VECTOR 28030.

The probabilities are very interesting as well:

Probabilities are for inside the watch area.
2 or more tornadoes: 20%
10 or more severe wind events: 70%
10 or more severe hail events: 50%
6 or more combined severe hail/wind: >95%

In addition the latest SPC outlook (20z) just added a 2% tornado risk in southern New England. Currently there is one cell returning a mesocyclone signal in northwest MA.

Stay tuned.