MESOSCALE DISCUSSION 2263
   NWS STORM PREDICTION CENTER NORMAN OK
   1132 PM CST SAT DEC 19 2009
   
   AREAS AFFECTED...MA...CT...RI...LONG ISLAND OF NY
   
   CONCERNING...BLIZZARD 
   
   VALID 200532Z - 201000Z
   
   SWATH OF HEAVY SNOW WILL SHIFT MORE RAPIDLY NEWD ACROSS THE
   NORTHEAST DURING THE OVERNIGHT...AND SHOULD BE PRIMARILY OFFSHORE BY
   12Z. SNOWFALL RATES FROM 1 TO 2 IN/HR WILL REMAIN COMMON...WITH
   EMBEDDED BURSTS TO AROUND 3 IN/HR. HEAVY SNOW SHOULD BE MOST
   PERSISTENT FROM ERN LONG ISLAND TO ERN MA...INCLUDING THE BOSTON AND
   PROVIDENCE METRO AREAS. OCCASIONAL BLIZZARD CONDITIONS WILL CONTINUE
   FROM INVOF ERN LONG ISLAND SOUND ACROSS SERN MA...DIMINISHING
   TOWARDS 12Z.
   
   00Z GFS/NAM AND 03Z RUC GUIDANCE ARE CONSISTENT THAT 980 MB SURFACE
   CYCLONE CENTERED AROUND 200 ESE ACY WILL ACCELERATE E/NEWD AS
   ASSOCIATED SHORT WAVE TROUGH EJECTS EWD. THIS WILL RESULT IN STRONG
   LOW/MID-LEVEL FRONTOGENTICAL AND ISENTROPIC ASCENT SHIFTING MORE
   QUICKLY NE ACROSS SRN NEW ENGLAND AND ADJACENT OFFSHORE WATERS.
   THUS...HEAVY SNOW WILL LIKELY BECOME CONFINED TO COASTAL AREAS OF
   SRN NEW ENGLAND BY 12Z. IN THE MEANTIME...INTENSE LIFT WITHIN THE
   DENDRITIC GROWTH ZONE AND WEAK ELEVATED INSTABILITY WILL SUPPORT
   WIDESPREAD 1 TO 2 IN/HR RATES WITH LOCALIZED CONVECTIVE BURSTS UP TO
   3 IN/HR.
   
   OCCASIONAL BLIZZARD CONDITIONS WILL PEAK DURING THE OVERNIGHT ACROSS
   SERN MA/SRN RI/ERN LONG ISLAND WHERE THE TIGHTEST SURFACE PRESSURE
   GRADIENT AND 50-60 KT N/NELYS AT 1 KM AGL LIKELY PERSIST /BASED ON
   UPTON NY VWP DATA AND MODEL FORECAST SOUNDINGS/. LOW-LEVEL FLOW
   SHOULD WEAKEN TOWARDS 12Z...RESULTING IN IMPROVING CONDITIONS.
   
   ..GRAMS.. 12/20/2009
   
   
   ...NOTICE...
   SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
   SCHEDULED BASIS FROM DECEMBER 1 THROUGH FEBRUARY 28...FOUR
   TIMES A DAY...AROUND 00 UTC...06 UTC...12 UTC...AND 18 UTC
   FOR SIGNIFICANT SHORT RANGE WINTER WEATHER EVENTS.
   
   ATTN...WFO...GYX...BOX...OKX...ALY...
   
   LAT...LON   40817227 40507384 40817399 41467356 42227264 42667174
               42847087 42697041 42087002 41716984 41247001 41157119
               40817227