MESOSCALE DISCUSSION 0653
   NWS STORM PREDICTION CENTER NORMAN OK
   1203 PM CDT FRI MAY 01 2009
   
   AREAS AFFECTED...CENTRAL/EASTERN PORTIONS OF VA/MD AND DE/NORTHERN
   NC
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 011703Z - 011900Z
   
   A SEVERE THREAT SHOULD DEVELOP/INCREASE THROUGH EARLY/MID AFTERNOON
   ACROSS THE CENTRAL/EASTERN PORTIONS OF VA/MD AND NORTHERN NC INTO
   PERHAPS DE...WITH THE PRIMARY RISKS OF DAMAGING WINDS AND SOME HAIL.
   THE NEED FOR A WATCH IS UNCLEAR...BUT CONVECTIVE TRENDS WILL BE
   CLOSELY MONITORED FOR THE POSSIBILITY OF A WATCH.
   
   EARLY MORNING UPPER AIR ANALYSIS AND CURRENT WATER VAPOR IMAGERY
   REFLECTS A LOW AMPLITUDE SHORTWAVE TROUGH CROSSING THE NORTH CENTRAL
   APPALACHIANS EARLY THIS AFTERNOON. THE DOWNSTREAM AIRMASS ACROSS THE
   CENTRAL/EASTERN PORTIONS OF VA/MD AND NC CONTINUES TO DIURNALLY
   DESTABILIZE AS TEMPERATURES/DEWPOINTS INCREASE THROUGH THE 70S/LOWER
   60S F RESPECTIVELY AMIDST MODERATE CLOUD BREAKS. WITH WEAKENING
   SURFACE CINH/DEEPENING CUMULIFORM DEVELOPMENT AND IMPLIED LARGE
   SCALE ASCENT CROSSING THE SPINE OF THE APPALACHIANS AT MIDDAY...IT
   SEEMS PROBABLE THAT AN UPSWING IN TSTM COVERAGE/INTENSITY SHOULD
   OCCUR THROUGH THE 18-20Z TIMEFRAME ALONG/AHEAD OF THE ADVANCING
   SYNOPTICALLY AIDED LEE TROUGH. WITH UP TO 35-40 KT OF MID LEVEL FLOW
   PER 12Z OBSERVED IAD/RNK/APG RAOBS AND MORE RECENT WSR-88D VWP
   DATA...A FEW SUPERCELLULAR STRUCTURES/PERHAPS A BRIEF TORNADO CANNOT
   BE RULED OUT...BUT THE PRIMARY CONVECTIVE MODE SHOULD BE
   MULTICELLULAR/LINEAR CLUSTERS CAPABLE OF DAMAGING WINDS AND SOME
   HAIL. ALTHOUGH THE EXTENT/MAGNITUDE OF THE SEVERE RISK IS A BIT
   UNCERTAIN...WILL CLOSELY MONITOR DEVELOPMENTAL TRENDS FOR THE
   POSSIBILITY OF A WATCH.
   
   ..GUYER.. 05/01/2009
   
   
   ATTN...WFO...PHI...AKQ...LWX...RAH...RNK...
   
   LAT...LON   35847768 35207992 36187986 38097774 39767597 39107487
               36727653 35847768