MESOSCALE DISCUSSION 1733
   NWS STORM PREDICTION CENTER NORMAN OK
   1106 AM CDT FRI JUL 31 2009
   
   AREAS AFFECTED...NRN VA...CNTRL/ERN MD...DE...SERN PA...CNTRL/SRN NJ
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 311606Z - 311730Z
   
   LEADING BATCH OF ENHANCED WARM ADVECTION AND ASSOCD ISOLD SVR THREAT
   CONTINUES NEWD TOWARD WRN NEW ENGLAND EARLY THIS AFTN.  HOWEVER...A
   SECONDARY SVR THREAT AREA APPEARS TO BE EVOLVING FARTHER TO THE S
   AND RISKS FOR DMGG WIND GUSTS AND PERHAPS AN ISOLD TORNADO WILL
   INCREASE FROM NRN VA TO SERN PA/CNTRL NJ THROUGH THE AFTN.
   
   LARGE BATCH OF CLOUDS/PCPN FROM CNTRL PA TO THE CNTRL APLCNS WERE
   BEING DRIVEN BY MODEST H85-H7 CONVERGENCE AND A MCV ROTATING THROUGH
   THE WV/MD PNHDLS.  DOWNSTREAM...VERY MOIST AIR MASS HAS HEATED
   CONSIDERABLY INTO THE LWR-MID 80S...RESULTING IN MLCAPES OF
   1000-1500 J/KG.  DIFFERENTIAL HEATING ALONG ERN EDGE OF THE UPSTREAM
   CLOUDS AND VARIOUS MESOSCALE BOUNDARIES EAST OF THE HIGHER TERRAIN
   WERE ALREADY THE FOCI FOR SFC-BASED CU/TCU.  EXPECT AS THE SECONDARY
   MID-LVL JET STREAK...ANALYZED OVER NC/VA PER VWPS...EJECTS
   NEWD...MODEST LARGER SCALE FORCING FOR ASCENT WILL AID IN SLOWLY
   EVOLVING TSTMS.
   
   HODOGRAPHS ARE EXPECTED TO BE SUBSTANTIALLY UNIDIRECTIONAL SSWLY
   ACROSS THE WARM SECTOR.  THIS SHOULD LEAD TO MAINLY SMALL-SCALE
   LINEAR STRUCTURES/BOWS GIVING LOCAL DMGG WIND GUSTS. 
   HOWEVER...RISKS FOR BRIEF ISOLD TORNADOES CANNOT BE RULED
   OUT...ESPECIALLY INVOF STORM SCALE BOUNDARIES/SFC LOWS. 
   ADDITIONALLY...VERY MOIST CONDITIONS /H85 DEW POINTS IN EXCESS OF 13
   DEG C/ AND LARGELY PARALLEL MEAN WIND FIELDS WILL BE FAVORABLE FOR
   VERY HEAVY/TRAINING RNFL WITH RATES EXCEEDING 1-2 INCHES PER HOUR AT
   TIMES.
   
   ..RACY.. 07/31/2009
   
   
   ATTN...WFO...PHI...AKQ...CTP...LWX...
   
   LAT...LON   38657770 39307714 39817668 40157627 40407600 40657545
               40537471 40357435 40187407 39847407 39357434 38917480
               38587519 38157555 37947578 37657626 37497658 37457694
               37527751 37617779 37857800 38057795 38657770