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Mesoscale Discussion 89
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   MESOSCALE DISCUSSION 0089
   NWS STORM PREDICTION CENTER NORMAN OK
   0524 PM CST SAT FEB 21 2015

   AREAS AFFECTED...PORTIONS OF FAR NRN VA...CNTRL MD...SERN PA...AND
   NWRN NJ

   CONCERNING...HEAVY SNOW 

   VALID 212324Z - 220330Z

   SUMMARY...MODERATE TO HEAVY SNOW WILL CONTINUE THROUGH 02-03Z BEFORE
   DIMINISHING LATER THIS EVENING. SNOWFALL RATES UP TO 1 INCH PER HOUR
   WILL CONTINUE TO BE POSSIBLE.

   DISCUSSION...23Z REGIONAL WSR-88D MOSAIC INDICATES AN EXPANSIVE AREA
   OF MDT-HVY PCPN CONTINUES TO EXPAND NEWD ACROSS THE MID-ATLANTIC AND
   INTO THE NORTHEAST/NEW ENGLAND. THIS EXPANSION IS IN RESPONSE TO
   CONTINUED STRONG ISENTROPIC ASCENT ON THE NOSE OF A 75-KT LLJ.
   REGIONAL VWP DATA ARE CHARACTERIZED BY LONG CYCLONICALLY LOOPING
   HODOGRAPHS...INDICATIVE OF THE ROBUST WAA ONGOING ACROSS THE REGION.
   IN CONCERT WITH LARGE-SCALE FORCING FOR ASCENT FROM AN APPROACHING
   MID-LEVEL SHORTWAVE TROUGH...THIS STRONG WAA WILL SUPPORT CONTINUED
   SNOWFALL RATES UPWARDS OF 1 INCH PER HOUR ACROSS THE MCD AREA.

   THE SNOW WILL LIKELY MIX WITH AND CHANGE OVER TO SLEET/FZRA ACROSS
   SRN/ERN PORTIONS OF THE AREA OVER THE NEXT FEW HOURS...AS THE WARM
   NOSE ALOFT CONTINUES TO SPREAD NE. THE 12Z WRF-NSSL IS IN AGREEMENT
   WITH THIS REASONING...AND ITS DEPICTION OF THE P-TYPE TRANSITION IS
   WELL SUPPORTED BY CURRENT DUAL-POLARIZATION DATA/MPING REPORTS. BY
   LATE THIS EVENING INTO EARLY TONIGHT...PCPN WILL GRADUALLY DECREASE
   IN INTENSITY...AS FORCING FOR ASCENT WEAKENS AND DEPARTS TO THE
   E/NE.

   ..PICCA/EDWARDS.. 02/21/2015


   ATTN...WFO...PHI...CTP...LWX...

   LAT...LON   39287647 38907731 38647780 39157796 39697735 40137662
               40747547 40927495 40987471 40797449 40217476 39647558
               39257646 39287647 

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Page last modified: February 22, 2015
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