MESOSCALE DISCUSSION 1055
   NWS STORM PREDICTION CENTER NORMAN OK
   0140 AM CDT THU JUN 13 2013

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

   CONCERNING...SEVERE THUNDERSTORM WATCH 302...

   VALID 130640Z - 130845Z

   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 302
   CONTINUES.

   SUMMARY...LARGE BOW ECHO AND ACCOMPANYING MCS IS EXPECTED TO
   MAINTAIN THREAT OF DAMAGING WIND ACROSS REMAINDER SRN/ERN OH INTO
   MTNS OF WV AND SRN PA THROUGH AT LEAST 10Z...WHICH IS SCHEDULED WW
   EXPIRATION TIME.  BEYOND THAT...ACROSS PIEDMONT AND TOWARD ATLC
   COAST...CONTINUITY OF TSTM COMPLEX AND THEREFORE OF WIND RISK IS
   MORE UNCERTAIN.  MORE WIDELY SCATTERED/SPORADIC SVR CONCERN EXISTS
   WITH PRECURSORY TSTMS OVER PORTIONS WV/PA. CONVECTIVE/INSTABILITY
   TRENDS WILL BE MONITORED AND NEW WW MAY BE NEEDED BEFORE
   10Z...BETWEEN MAIN MCS AND ATLC COAST.

   DISCUSSION...06Z SFC MESOANALYSIS SHOWS LOW OVER WRN
   LE...CORRESPONDING TO COMMA-HEAD FEATURE OF BOW.  ACCOMPANYING WARM
   FRONT WAS DRAWN FROM LOW ESEWD ACROSS NWRN OH AND W-CENTRAL/SRN PA
   NEAR LINE FROM LPR...BTP...THV...PHL..THEN SEWD OVER CAPE MAY AREA. 
   WARM FRONT WAS ILL-DEFINED ACROSS MUCH OF PA BECAUSE OF ONGOING
   CONVECTION...WHICH MAY IMPEDE ALREADY SLOW NWD PROGRESS OF FRONT. 
   MOST FAVORABLE AIR MASS WILL REMAIN S OF FRONT...ON EITHER SIDE OF
   RELATIVE LOW-LEVEL THETAE MIN ANALYZED ALONG CREST OF APPALACHIANS. 
   CORRIDOR OF UPPER 60S TO LOW 70S F SFC DEW POINTS AHEAD OF MCS...AND
   S OF FRONT...WILL SUPPORT PRE-STORM MLCAPE AROUND 2500 J/KG OVER SRN
   OH...TO AROUND 1000 J/KG ALONG WARM FRONT NEAR OH/PA BORDER...AMIDST
   40-50 KT EFFECTIVE SHEAR VECTORS ALIGNED NEARLY ORTHOGONAL WITH
   RESPECT TO LEADING/ERN EDGE OF BOW.  MODIFIED MODEL SOUNDINGS
   SUGGEST MLCINH WILL REMAIN MINIMAL W OF MTNS...AND PERHAPS EVEN OVER
   HIGHER TERRAIN OF WV...DUE TO OFFSETTING OF SFC DIABATIC COOLING BY
   LOW-LEVEL MOISTURE TRANSPORT AND THETAE ADVECTION NEAR SFC AND INVOF
   WLY LLJ.

   AS FOR MEASURED WIND...CONVECTION HAS BEEN PRODUCING PRIMARILY
   SUB-SVR GUSTS -- MOSTLY 30-45 KT -- WHILE PASSING ACROSS OBSERVATION
   SITES IN ITS PATH.  WHILE SVR GUSTS AOA 50 KT ARE POSSIBLE...THEY
   SHOULD BE LOCALIZED AROUND CELL-SCALE ACCELERATIONS AND
   PROCESSES...SUCH AS LEWPS AND EMBEDDED MISOVORTICES. 
   NONETHELESS...WINDS BELOW SVR CRITERIA STILL MAY DAMAGE
   TREES...POWER LINES AND EXTERIOR OF STRUCTURES.  BRIEF/SMALL TORNADO
   CANNOT BE RULED OUT WITH SUCH LOCALIZED MISOVORTICES...HOWEVER
   DOMINANT RISK IS FOR DAMAGING DOWNDRAFT GUSTS.

   ..EDWARDS.. 06/13/2013


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

   LAT...LON   39538483 39568329 40078229 40738174 41218154 41598149
               41848093 41968030 40847689 39837407 39327445 39157466
               38917484 38937502 38807509 38477503 38007524 37747552
               37307578 37167593 36897606 37627852 38698253 39338460
               39538483