MESOSCALE DISCUSSION 0803
   NWS STORM PREDICTION CENTER NORMAN OK
   0208 PM CDT WED MAY 18 2011
   
   AREAS AFFECTED...MID ATLANTIC STATES NWWD THROUGH UPPER OH VALLEY
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 305...
   
   VALID 181908Z - 182015Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 305
   CONTINUES.
   
   DAY 1 SLIGHT RISK AREA WILL BE EXPANDED WNWWD INTO NRN OH AND ALSO
   NEWD ACROSS PARTS OF ERN PA AND NJ.  FOR ERN PA/NJ SHORT TERM SEVERE
   WEATHER THREAT...REFER TO SPC MCD 802.
   
   ...NRN OH AND UPPER OH VALLEY...
   AT 19Z...REGIONAL RADAR IMAGERY SHOWED AREAS OF TSTMS EXTENDING FROM
   NRN VA...ERN WV NWWD THROUGH WRN PA AND ERN/NERN OH.  ALTHOUGH
   INSTABILITY ACROSS MUCH OF THIS REGION REMAINS SOMEWHAT MARGINAL
   /MUCAPE 500-1200 J PER KG/...FORCING FOR ASCENT ATTENDANT TO A
   COMPACT SHORTWAVE TROUGH ROTATING NNWWD ACROSS WV AT THIS TIME IS
   LIKELY COMPENSATING AND AIDING IN STRONGER STORM DEVELOPMENT OVER
   THE UPPER OH VALLEY.  THIS TREND WILL CONTINUE AS THIS MID-UPPER
   LEVEL FEATURE MOVES THROUGH WRN PA AND OH...WHERE VISIBLE SATELLITE
   IMAGERY HAS SHOWN BREAKS IN THE CLOUDS FOR GREATER SURFACE HEATING
   INVOF A NWWD EXTENDING SURFACE TROUGH.  
   
   ...SRN AND ERN PARTS OF WW 305...
   WATER VAPOR IMAGERY SHOWED A SECOND SHORTWAVE TROUGH TRACKING NNWWD
   TOWARD THE DELMARVA/CHESAPEAKE BAY REGION WITH AN ATTENDANT 50 KT
   SSELY MIDLEVEL JET.  INSTABILITY IS GREATER ACROSS THE SRN/ERN PARTS
   OF WW 305.  THIS COMBINED WITH EFFECTIVE BULK SHEAR 35-45 KT WILL
   MAINTAIN A POTENTIAL FOR SUPERCELLS.
   
   ..PETERS.. 05/18/2011
   
   
   ATTN...WFO...OKX...PHI...BGM...AKQ...CTP...LWX...RNK...PBZ...
   RLX...CLE...
   
   LAT...LON   41358337 41478273 41678095 40947883 40907868 40757726
               41537652 41837598 41697526 40917407 40167402 39447432
               39307465 38177511 37067586 37627797 37637895 38058035
               38648039 39598126 40298138 40848342 41358337