MESOSCALE DISCUSSION 0124
   NWS STORM PREDICTION CENTER NORMAN OK
   0351 PM CST FRI FEB 08 2013
   
   AREAS AFFECTED...SRN NEW ENGLAND...LONG ISLAND AND SRN NY...FAR NERN
   NJ
   
   CONCERNING...HEAVY SNOW 
   
   VALID 082151Z - 090145Z
   
   SUMMARY...SNOWFALL RATES ARE EXPECTED TO INCREASE MARKEDLY THIS
   EVENING ...WITH RATES OF 1-2 INCHES PER HR OVER SRN NY/NERN NJ...TO
   2-3 INCHES ACROSS SRN NEW ENGLAND. ADDITIONALLY...STRENGTHENING
   WINDS MAY RESULT IN LOCALIZED BLIZZARD CONDITIONS...ESPECIALLY NEAR
   THE COAST.
   
   DISCUSSION...SFC OBS FROM 21Z CONTINUE TO REFLECT A RAPIDLY
   DEEPENING OFFSHORE CYCLONE...WITH PRESSURE FALLS OF 3-4 MB/HR
   OBSERVED. RADAR REFLECTIVITY MOSAIC SHOWS HIGHER PRECIPITATION RATES
   ARE BEGINNING TO SPREAD INLAND ACROSS LONG ISLAND AND TOWARDS RI/SRN
   MA/SRN CT. HOWEVER...SOME BRIGHT-BAND ENHANCEMENT MAY BE OCCURRING
   AS MIXED P-TYPE OF RAIN AND/OR SNOW IS PREDOMINANT ACROSS LONG
   ISLAND...WHERE SFC TEMPERATURES ARE CURRENTLY RANGING FROM 33-35 F.
   INITIALLY...NEAR- OR ABOVE-FREEZING TEMPERATURES MAY SUPPRESS RATES
   IMMEDIATELY ALONG THE COAST...BUT WITH LOW-LEVEL COLD ADVECTION
   INCREASING AS THE CYCLONE TRACKS N-NE...A CHANGEOVER TO
   PREDOMINANTLY SNOW IS EXPECTED WITHIN THE NEXT 2-3 HRS ACROSS MOST
   OF THE HIGHLIGHTED AREA.
   
   SNOWFALL RATES WILL BE INCREASING IN CONCERT WITH INTENSE ISENTROPIC
   LIFT AND LOW-LEVEL FRONTOGENESIS WITHIN A DEFORMATION ZONE.
   ADDITIONALLY...AN UPSTREAM SHORTWAVE UPPER TROUGH /LOCATED OVER THE
   UPPER OH VALLEY PER 2130Z WATER VAPOR IMAGERY/ IS FORECAST TO PHASE
   WITH THE OFFSHORE DEEP-LAYER CYCLONE. AS THIS OCCURS...THE
   COMBINATION OF STRONG MIDLEVEL HEIGHT FALLS AND UPPER DIVERGENCE
   WITHIN A COUPLED UPPER JET STRUCTURE WILL CONTRIBUTE TO INCREASING
   DEEP-LAYER ASCENT. FORECAST MODEL SOUNDINGS SHOW A NEARLY SATURATED
   COLUMN WITH A DEEP ISOTHERMAL LAYER LOCATED BENEATH THE DENDRITIC
   GROWTH ZONE. THESE FACTORS WILL BE FAVORABLE FOR EXTREMELY HIGH
   SNOWFALL RATES...ESPECIALLY FROM ERN LONG ISLAND INTO SRN NEW
   ENGLAND...INCLUDING THE BOSTON METRO AREA...AS SUPPORTED BY THE
   RECENT SUITE OF HIGH-RESOLUTION NUMERICAL GUIDANCE.
   
   ..ROGERS.. 02/08/2013
   
   
   ATTN...WFO...GYX...BOX...OKX...ALY...PHI...
   
   LAT...LON   41487041 41157173 40917237 40527347 40487426 40887445
               41967427 42867373 43097258 43197147 43017087 42627073
               42117042 41487041