MESOSCALE DISCUSSION 1056
   NWS STORM PREDICTION CENTER NORMAN OK
   0427 AM CDT THU JUN 13 2013

   AREAS AFFECTED...PORTIONS EXTREME SRN OH...WV...NRN/CENTRAL/ERN
   VA...PA...DC...DE...NJ...MD.

   CONCERNING...SEVERE THUNDERSTORM WATCH 302...303...

   VALID 130927Z - 131130Z

   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
   302...303...CONTINUES.

   SUMMARY...BROADLY BOWING MCS AND TRAILING COLD POOL WILL CONTINUE TO
   FORWARD-PROPAGATE ESEWD ACROSS DISCUSSION AREA THROUGH REMAINDER
   MORNING.  SOME UNCERTAINTY STILL EXISTS AS TO RE-STRENGTHENING OF
   MRGLLY SVR/DAMAGING COMPLEX NOW OVER WRN PA AND NRN/WRN WV...ONCE IT
   GOES E OF MTNS...GIVEN THAT PASSAGE OF RELATED BOUNDARY SHOULD OCCUR
   OVER PIEDMONT/COASTAL PLAIN PRIOR TO SUBSTANTIAL SFC DIABATIC
   HEATING.  SFC MEASURING STATIONS OVER WHICH COMPLEX HAS PASSED
   DURING PAST FEW HOURS STILL HAVE RECORDED SUB-SVR GUSTS BELOW 50 KT.
    HOWEVER...WW 303 SHOULD BE MAINTAINED ALONG/AHEAD OF MCS...AS WELL
   AS FOR SPORADIC SVR WIND/HAIL RISK FROM PRECURSORY CONVECTION.  WW
   302 MAY BE ALLOWED TO EXPIRE AS SCHEDULED OVER MOST OF ITS COVERAGE
   AREA...BUT ALSO MAY BE EXTENDED IN TIME FOR PRECONVECTIVE AREAS
   STILL IN WW 302.

   DISCUSSION...DIFFUSE SFC WARM FRONT WAS ANALYZED AHEAD OF MCS...FROM
   W-CENTRAL PA ESEWD ACROSS SERN PA AND SRN NJ.  WARM FRONT SHOULD
   DRIFT NWD...AND APPEARS TO BE SHALLOW ENOUGH THAT AT LEAST MRGL
   POTENTIAL FOR DAMAGING GUSTS EXTENDS TO ITS N.  AIR MASS S OF FRONT
   IS COMMONLY CHARACTERIZED BY SFC DEW POINTS UPPER 60S TO LOW 70S F
   IN LOWER ELEVATIONS...YIELDING WEAKLY CAPPED MLCAPE 1000-2000 J/KG
   IN MODIFIED FCST SOUNDINGS.  WEAK CINH MEANS AIR MASS IS QUITE PRONE
   TO FORCED ASCENT ALONG LEADING EDGE OF COLD POOL...WITH POTENTIAL
   FOR CONTINUED CONVECTIVE DEVELOPMENT BEHIND GUST FRONT.  INCREASING
   CINH IS EVIDENT E OF MTNS AND GENERALLY NE OF POTOMAC RIVER...THOUGH
   COMBINATION OF LOW-LEVEL THETAE ADVECTION AND WEAK/PRECONVECTIVE SFC
   DIABATIC HEATING MAY ERODE ENOUGH CAPPING TO SUPPORT TSTM
   MAINTENANCE EWD TO NEAR COAST.  CONVECTIVE AND INSTABILITY TRENDS
   WILL BE MONITORED FOR POSSIBLE WW E OF WW 303.

   ..EDWARDS.. 06/13/2013


   ATTN...WFO...PHI...BGM...AKQ...CTP...LWX...RNK...PBZ...RLX...
   ILN...

   LAT...LON   38748314 38988258 39128183 39358084 39777992 40677943
               41407938 41817940 41927702 41237546 40617486 39717422
               38917484 38937502 38807509 38477503 38007524 37747552
               37307578 37737802 38458214 38558347 38748314