MESOSCALE PRECIPITATION DISCUSSION 0170
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
337 PM EDT MON JUL 22 2013
 
AREAS AFFECTED...MUCH OF WV...SOUTHWEST PA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 221936Z - 222336Z
 
SUMMARY...A BROKEN BAND OF THUNDERSTORMS WITH HEAVY RAINFALL RATES
IS MOVING INTO AN AREA WITH LOW FLASH FLOOD GUIDANCE VALUES --
FFGS -- ACROSS WV AND SOUTHWEST PA.  FLASH FLOODING IS POSSIBLE IN
THIS REGION.

DISCUSSION...A BAND OF CONVECTION IS MOVING INTO/TOWARDS WV AT
THIS TIME, WITH SCATTERED THUNDERSTORMS ONGOING ACROSS SOUTHWEST
PA.  THIS ACTIVITY IS FOCUSED NEAR A SURFACE TROUGH/OUTFLOW
BOUNDARY MOVING INTO THE AREA FROM OHIO.  DIVERGENCE ALOFT IS
BEING AIDED BY A SHORTWAVE MOVING ACROSS IN AND SOUTHERN MI.  
AHEAD OF THE BAND, 850 HPA WINDS ARE ON THE ORDER OF 30 KNOTS,
WHICH ARE INTERACTING WITH PRECIPITABLE WATER VALUES -- PWS -- OF
NEAR TWO INCHES.  THIS SETUP SHOULD ALLOW FOR CONTINUED
ORGANIZATION OF CONVECTION IN THIS REGION.  THE PWS ARE BETWEEN
THE 80TH AND 90TH PERCENTILES FOR THE REGION FOR LATE JULY, WHICH
ADDS TO THE FLASH FLOOD POTENTIAL.  CAPE VALUES ARE BETWEEN
1000-1500 J/KG ACROSS WV.  THE MAIN PRECIPITATION BAND HAS A
HISTORY OF PRODUCING 1.5-2 INCHES OF RAINFALL WITHIN A FEW HOURS,
WHICH WOULD SLIGHTLY EXCEED THE FFGS ACROSS THE REGION. 
CONSIDERING THE ABOVE, BELIEVE THE CONVECTIVE BAND WILL CONTINUE
MOVING ALONG WITH LITTLE CHANGE IN INTENSITY OVER THE NEXT SEVERAL
HOURS.  A QUICK 2 INCHES OF RAINFALL IS EXPECTED, WHICH COULD LEAD
TO REGIONAL FLASH FLOODING.

ROTH

ATTN...WFO...LWX...RNK...PBZ...RLX...JKL...

ATTN...RFC...LMRFC...MARFC...OHRFC...

LAT...LON   37748230 37998250 38878193 40148117 40808069 40497951
            38667950 37268092 37748230