MESOSCALE DISCUSSION 0431
   NWS STORM PREDICTION CENTER NORMAN OK
   0459 PM CDT WED APR 10 2013
   
   AREAS AFFECTED...PORTIONS PA...ERN OH...NRN WV PANHANDLE...SERN
   NY...NRN NJ.
   
   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 
   
   VALID 102159Z - 102300Z
   
   PROBABILITY OF WATCH ISSUANCE...80 PERCENT
   
   SUMMARY...TWO PRIMARY/BOWING TSTM COMPLEXES -- ONE MOVING NEWD OUT
   OF NERN PA...SECOND MOVING EWD FROM NERN OH -- ARE FCST TO OFFER
   DAMAGING WIND POTENTIAL.  EASTERN ONE WILL BE SHORTER-LIVED...MOVING
   INTO MORE STABLE AIR.  WESTERN COMPLEX MAY PERSIST WITH SVR THREAT
   RELATIVELY MAXIMIZED NEAR OUTFLOW BOUNDARY FROM FIRST.  ISOLATED TO
   WIDELY SCATTERED TSTMS ALONG THEIR OUTFLOW BOUNDARIES MAY PRODUCE
   OCNL HAIL AND GUSTS NEAR SVR LIMITS...BUT THREAT FROM THOSE APPEARS
   MRGL/TRANSIENT.  ELEVATED CONVECTION WELL N OF BOUNDARY SHOULD
   REMAIN LARGELY SUB-SVR...BUT WITH ISOLATED HAIL NEAR SVR LIMITS AND
   STG GUSTS.  NEW WW IS BEING CONSIDERED THAT WOULD COVER WRN COMPLEX.
   
   DISCUSSION...SFC MESOANALYSIS INDICATED COLD MARINE BOUNDARY FROM
   NEAR ACY NNWWD ACROSS BUCKS COUNTY PA THAN ARCHING OVER PIKE COUNTY
   PA AND SULLIVAN COUNTY NY...HAVING ALREADY PASSED MSV.  THIS
   BOUNDARY  CORRESPONDS WELL TO FINE LINE EVIDENT IN COMPOSITE
   REFLECTIVITY ANIMATIONS...MOVING WWD 5-10 KT.  THIS BOUNDARY WILL BE
   OVERTAKEN WITHIN NEXT 1-2 HOURS FROM N-S...BY MCS MOVING EWD 45-50
   KT OVER NERN PA.  QUASISTATIONARY FRONT INTERSECTED MCS OVER NERN PA
   NEAR BORDER WITH SULLIVAN COUNTY NY...AND EXTENDED ENEWD ACROSS SWRN
   MA.  NARROW PLUME OF RELATIVELY UNDISTURBED WARM SECTOR WITH AT
   LEAST MRGLLY SFC-BASED EFFECTIVE INFLOW PARCELS IS EVIDENT BETWEEN
   LEADING MCS AND MARINE BOUNDARY...WITHIN WHICH MCS STILL POSES RISK
   OF STG-DAMAGING GUSTS.  THIS RISK WILL DIMINISH SUBSTANTIALLY WITH
   EWD EXTENT INTO STABLE MARINE AIR...THOUGH BRIEF/ISOLATED
   PENETRATION OF CONVECTIVE GUSTS TO SFC CANNOT BE RULED OUT AS FAR E
   AS HUDSON RIVER.
   
   OUTFLOW BOUNDARY FROM NERN PA COMPLEX WAS ANALYZED ACROSS
   NORTHUMBERLAND/CAMBRIA/BEAVER COUNTIES PA INTO ERN OH...INTERSECTING
   NEXT MCS BETWEEN CAK-PHD.  SECOND COMPLEX EXHIBITS VERY SIMILAR
   STRUCTURE AND MOVEMENT TO FIRST...BUT MORE INTENSE...PRODUCING GUSTS
   TO 56 KT AT POV AT 2117Z.  ITS DAMAGING-WIND THREAT SHOULD DIMINISH
   WITH NWD EXTENT FROM OUTFLOW BOUNDARY...WHERE STABLE LAYER BECOMES
   PROGRESSIVELY COOLER AND DEEPER.  NONETHELESS...60-80 KT REAR-INFLOW
   JET WAS EVIDENT IN CLE RADAR BASE VELOCITY DATA...INDICATING
   CONSIDERABLE MOMENTUM FOR WIND POTENTIAL TO PERSIST INTO WRN PA. 
   NEAR AND S OF OUTFLOW BOUNDARY...AIR MASS IS CHARACTERIZED BY
   SPORADICALLY WELL-MIXED BOUNDARY LAYERS AWAY FROM SMALLER
   OUTFLOWS...SUPPORTING THREAT FOR SVR GUSTS.  HOWEVER...DIABATIC SFC
   COOLING WILL STABILIZE THIS AIR MASS WITH TIME AND REDUCE ALREADY
   MRGL MLCAPE OF AROUND 500 J/KG.  AS SUCH...DAMAGING GUST POTENTIAL
   SHOULD DIMINISH WITH TIME AND EWD EXTENT ACROSS CENTRAL-ERN PA.
   
   ..EDWARDS/CORFIDI.. 04/10/2013
   
   
   ATTN...WFO...OKX...PHI...BGM...CTP...PBZ...CLE...
   
   LAT...LON   40298197 40988109 41718071 41757850 41657496 41237394
               40347407 39997552 39767897 40298197