MESOSCALE DISCUSSION 0793
   NWS STORM PREDICTION CENTER NORMAN OK
   0734 AM CDT FRI MAY 21 2004
   
   AREAS AFFECTED...NRN VA/MUCH OF MD
   
   CONCERNING...SEVERE THUNDERSTORM POTENTIAL 
   
   VALID 211234Z - 211400Z
   
   FORWARD PROPAGATING MCS SHOULD CONTINUE TO MOVE SEWD AT 35-40 KT
   ACROSS NRN VA AND WRN INTO CENTRAL MD THROUGH 14Z WITH MOST WIND
   GUSTS RANGING FROM 30-40 KT...AND ISOLATED GUSTS AT OR EXCEEDING
   SEVERE LEVELS POSSIBLE.
   
   REGIONAL RADARS SHOW THE LEADING EDGE OF A WELL ESTABLISHED COLD
   POOL EXTENDING FROM SOUTH CENTRAL PA SWWD ALONG THE FAR ERN WV
   PANHANDLE AT 1230Z.  DOWNSTREAM AIR MASS IS MARGINALLY UNSTABLE WITH
   MUCAPE RANGING FROM 1000-1500 J/KG.  VIS IMAGERY SHOWS A WIDESPREAD
   LOW-LEVEL CLOUD SHIELD WITH SURFACE OBSERVATIONS SHOWING FOG ACROSS
   NRN VA EWD TO DE.  SATELLITE IMAGERY ALSO SHOWS UPPER LEVEL CLOUD
   SHIELD WITH MCS HAS OVERSPREAD DOWNSTREAM OF THE SQUALL LINE...
   INDICATING SURFACE HEATING AND ADDITIONAL DESTABILIZATION WILL BE
   LIMITED.  DESPITE SEWD MOVEMENT OF STORMS AT UP TO 40 KT...STABLE
   BOUNDARY LAYER PER VIS IMAGERY/AREA 12Z RAOBS IS EXPECTED TO LIMIT
   THE DOWNWARD MOMENTUM TRANSFER OF THIS WIND SPEED...AS THESE STORMS
   REMAIN SLIGHTLY ELEVATED.
   
   ..PETERS.. 05/21/2004
   
   
   ATTN...WFO...AKQ...CTP...LWX...
   
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