MESOSCALE DISCUSSION 0900
   NWS STORM PREDICTION CENTER NORMAN OK
   0357 AM CDT SUN MAY 27 2007
   
   AREAS AFFECTED...S-CNTRL OK INTO N-CNTRL TX
   
   CONCERNING...HEAVY RAINFALL 
   
   VALID 270857Z - 271100Z
   
   POTENTIAL FOR LOCALLY EXCESSIVE RAINFALL WITH HOURLY RATES
   APPROACHING 1.5 TO 2.0 INCHES IS EXPECTED TO CONTINUE FOR THE NEXT
   SEVERAL HOURS.
   
   CURRENT WATER VAPOR IMAGERY INDICATES A SLOW-MOVING...LARGE-SCALE
   TROUGH OVER THE SRN PLAINS EARLY THIS MORNING WITH A SMALLER
   SCALE...EMBEDDED VORTICITY MAXIMUM OVER SWRN/S-CNTRL OK.  THIS
   VORTICITY MAXIMUM HAS SHOWN LITTLE OR NO MOVEMENT OVER THE PAST
   SEVERAL HOURS...REMAINING 30-35 MILES E OF FSI...WITH ASSOCIATED
   TSTM CLUSTERS EXTENDING FROM GRADY...MCCLAIN AND CLEVELAND COUNTIES 
   IN OK SWD TO COOKE AND DENTON COUNTIES IN N-CNTRL TX AS OF 0845Z. 
   RUC FORECAST SOUNDINGS AND CURRENT PURCELL OK PROFILER INDICATE THAT
   AMBIENT ENVIRONMENT IS MOIST /PW OF AROUND 1.70 INCHES/ AND
   MARGINALLY UNSTABLE WITH RELATIVELY WEAK SLY FLOW THROUGH THE
   CLOUD-BEARING LAYER.  BASED ON 1- AND 3-HR RADAR ESTIMATES...THE
   SLOW STORM MOTIONS AND POTENTIAL FOR TRAINING ECHOES...HOURLY RAIN
   RATES OF 1.5-2.0 INCHES WILL BE POSSIBLE AT SOME LOCATIONS.
   
   LATEST SHORT TERM RUC AND NAM/WRF GUIDANCE SUGGESTS THAT
   ABOVEMENTIONED VORTICITY MAXIMUM AND ATTENDANT HEAVIER RAINFALL
   THREAT MAY TEND TO DRIFT SLOWLY NWD LATER THIS MORNING INTO CNTRL
   OK.
   
   ..MEAD.. 05/27/2007
   
   
   ATTN...WFO...FWD...OUN...
   
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