MESOSCALE DISCUSSION 0802
   NWS STORM PREDICTION CENTER NORMAN OK
   0134 PM CDT WED MAY 18 2011
   
   AREAS AFFECTED...PARTS OF ERN PA AND CENTRAL/NRN NJ
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 181834Z - 181930Z
   
   WW IS POSSIBLE THIS AFTERNOON ACROSS PARTS OF ERN PA AND CENTRAL/NRN
   NJ.  THIS POTENTIAL WILL BE GREATER IF INSTABILITY INCREASES BEYOND
   THE CURRENT MARGINAL VALUES AND RADAR TRENDS SUGGEST MORE PERSISTENT
   UPDRAFTS.
   
   SURFACE ANALYSES INDICATED A CORRIDOR OF GREATER MOISTURE EXTENDING
   INLAND FROM THE NJ COAST INTO ERN PA...WITH VALUES IN THE LOWER 60S
   ACROSS MUCH OF NJ INTO EAST CENTRAL/SERN PA AND NEAR 60 IN NERN PA. 
   ALTHOUGH CLOUDINESS HAS LIMITED SURFACE HEATING/ DESTABILIZATION AND
   WEAKER MIDLEVEL LAPSE RATES EXIST ACROSS THIS AREA...MUCAPE IS
   RANGING FROM 500-1000 J/KG.  THE MARGINAL INSTABILITY AND LAPSE
   RATES SUGGEST INDIVIDUAL STORMS MAY STRUGGLE TO ATTAIN PERSISTENT
   UPDRAFTS...AND THUS POSE A SUFFICIENT THREAT FOR STRONG TO SEVERE
   TSTM COVERAGE THAT WOULD WARRANT A SEVERE WEATHER WATCH.
   
   DESPITE THE MARGINAL INSTABILITY...KINEMATICS ARE FAVORABLE FOR
   STORM ORGANIZATION AND SOME ROTATION.  TRENDS IN LOW LEVEL FLOW PER
   OBJECTIVE ANALYSES AND AREA WSR-88D VWPS INDICATED AN INCREASE IN
   WIND SPEEDS WITH SOME BACKING TO SELY.  THIS IS RESULTING IN AN
   INCREASE IN LOW LEVEL SHEAR FOR STORM ROTATION.  STRONGER ESELY
   MIDLEVEL WINDS/DEEP SHEAR WILL CONTINUE TO INCREASE THIS AFTERNOON
   AS THE ATTENDANT CLOSED LOW LOCATED OVER THE CENTRAL APPALACHIANS
   SHIFTS NWD.  REGIONAL RADAR IMAGERY SHOWED AN AREA OF SHOWERS/
   EMBEDDED TSTMS EXTENDING FROM SERN PA THROUGH CENTRAL/NRN NJ AND
   OFFSHORE...WITH A FEW OF THE STORMS INDICATING PERIODIC LOW LEVEL
   ROTATIONAL COUPLETS.
   
   ..PETERS.. 05/18/2011
   
   
   ATTN...WFO...OKX...PHI...BGM...CTP...
   
   LAT...LON   39697423 39987539 40347657 40807703 41587662 41697574
               41317473 40887420 40457406 39827398 39697423