MESOSCALE DISCUSSION 2033
   NWS STORM PREDICTION CENTER NORMAN OK
   0205 PM CDT SUN AUG 21 2011
   
   AREAS AFFECTED...ERN MASSACHUSETTS...NEW HAMPSHIRE AND MAINE
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 795...
   
   VALID 211905Z - 212000Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 795
   CONTINUES.
   
   WW 795 MAY BE LOCALLY EXTENDED IN AREA EASTWARD ACROSS PARTS OF NEW
   ENGLAND.  AN ADDITIONAL WW COULD BECOME NECESSARY LATE THIS
   AFTERNOON FARTHER EAST.
   
   A VIGOROUS PRE-FRONTAL LINE OF STORMS HAS EVOLVED ACROSS WESTERN
   PORTIONS OF NEW ENGLAND...WITHIN A MOIST UNSTABLE ENVIRONMENT
   CHARACTERIZED BY MIXED LAYER CAPE ON THE ORDER OF 2000 J/KG.  DEEP
   LAYER SOUTHWESTERLY MEAN FLOW IS STILL SOMEWHAT MODEST ON THE ORDER
   OF 25-30 KT...BUT VERTICAL SHEAR...WHILE NOT STRONG...MAY BE
   SUFFICIENT FOR AT LEAST SHORT-LIVED UPDRAFT ROTATION IN STRONGER
   CELLS.  IT IS ALSO TENDING TO ALLOW ANVIL LEVEL CLOUD COVER AND
   PRECIPITATION TO ADVECT ACROSS AND IMPACT THE DOWNSTREAM LOW-LEVEL
   INFLOW LAYER...WHICH MAY ULTIMATELY LIMIT THE SEVERE THREAT ACROSS
   EASTERN AND NORTHERN NEW ENGLAND.  HOWEVER...THE ENVIRONMENT ACROSS
   THIS REGION HAS ALREADY RECEIVED CONSIDERABLE INSOLATION...AND
   LOW-LEVEL LAPSE RATES ARE FAIRLY STEEP...SO THE RISK FOR POTENTIALLY
   DAMAGING WIND GUSTS STILL CAN NOT BE RULED OUT AS STORMS SPREAD
   NORTH AND EAST OF WW 795.  THIS COULD IMPACT THE GREATER BOSTON
   METROPOLITAN AREA AND THE PORTLAND ME BY 21-22Z.
   
   ..KERR.. 08/21/2011
   
   
   ATTN...WFO...CAR...GYX...BOX...OKX...
   
   LAT...LON   42037265 42757162 44067167 45797001 44946923 43636995
               42187100 41097290 42037265