MESOSCALE DISCUSSION 2260
   NWS STORM PREDICTION CENTER NORMAN OK
   0557 AM CST SAT DEC 19 2009
   
   AREAS AFFECTED...ERN WV...NRN VA...MD...DE...SERN PA...NJ
   
   CONCERNING...HEAVY SNOW 
   
   VALID 191157Z - 191800Z
   
   BANDS OF HEAVY SNOW WITH RATES OF 1-2 IN/HR WILL PERSIST MAINLY FROM
   ERN WV ACROSS NRN VA AND MD...DE...SERN PA AND SRN NJ. THE LONGEST
   DURATION OF HEAVY SNOW RATES IS LIKELY TO BE OVER ERN WV...NRN
   VA...AND MUCH OF MD.
   
   A LARGE SHIELD OF SNOW CURRENTLY EXTENDS FROM NEAR THE UPPER LOW
   CENTER OVER WV EWD N OF A DEEPENING SURFACE LOW. WARM ADVECTION
   COUPLED WITH DEEP LAYER FRONTOGENESIS IS RESULTING IN PERSISTENT AND
   MULTIPLE W-E BANDS OF HEAVY SNOW. DUE TO THE SLOW MOVEMENT OF THE
   TROUGH...LONG DURATIONS OF HEAVY SNOW WILL OCCUR. THROUGH
   18Z...EXPECT A SLIGHT PIVOT OF THE SNOW BANDS TO A WSW-ENE
   ORIENTATION AS THE LOW LEVEL WINDS BACK A BIT. BROAD...PERSISTENT
   FRONTOGENESIS SHOULD RESULT IN FURTHER CONSOLIDATION OF THE SNOW
   BANDS OVER THE MCD AREA.
   
   AS THE UPPER LOW PIVOTS EWD...COOLING ALOFT MAINLY ABOVE 650 MB WILL
   RESULT IN A DEEPER DENDRITIC GROWTH LAYER YIELDING A MORE
   TEMPERATURE PROFILE FOR PARTICULARLY HEAVY SNOW FROM 12-18Z ACROSS
   ERN WV...NRN VA...AND CNTRL MD. SNOW RATES COULD INCREASE TO MORE
   THAN 2 IN/HR AT TIMES.
   
   ..JEWELL.. 12/19/2009
   
   
   ...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...OKX...PHI...AKQ...CTP...LWX...RNK...PBZ...RLX...
   
   LAT...LON   37787819 37668022 38068133 39008107 39627971 40377822
               40597660 40617420 39997393 38987476 38347589 37787819