MESOSCALE PRECIPITATION DISCUSSION 0243
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 PM EDT SAT AUG 02 2014
 
AREAS AFFECTED...WESTERN NY, WESTERN PA, EASTERN OH, WV 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 021856Z - 030056Z
 
SUMMARY...PULSE CONVECTION WITH HEAVY RAIN COULD COMPROMISE LOW
FLASH FLOOD GUIDANCE VALUES - FFGS - IN THE REGION. FLASH FLOODING
IS CONSIDERED POSSIBLE.

DISCUSSION...A REGION WITH PRECIPITABLE WATER VALUES ~1.25" EXISTS
NEAR A SURFACE-850 HPA BOUNDARY EXTENDING FROM EASTERN OH
SOUTHWARD INTO WV, WITH A SECOND BOUNDARY MOVING ACROSS LAKE
ONTARIO TOWARDS WESTERN NY.  INFLOW IS MINIMAL, INDICATING THAT
OUTFLOW-DOMINANT, CAPE-DRIVEN, PULSE CONVECTION IS EXPECTED, WHICH
IS CONFIRMED BY RECENT RADAR IMAGERY.  CAPE VALUES ARE CURRENTLY
BETWEEN 1000-2000 J/KG ACROSS EASTERNMOST OH, NORTHWEST PA, AND
NORTHWEST NY.

STORMS ARE EXPECTED TO MOVE NORTHEAST AT 15-20 KTS, MOVING WITH
THE MEAN 850-400 WIND FIELD, WHILE THE CONVECTIVE REGION MOVES
EASTWARD WITH TIME WITH ITS PARENT UPPER-LEVEL LOW.  THE 00Z-BASED
SSEO NEIGHBORHOOD PROBABILITIES SHOW AREAS WHICH HAVE A >50% OF
BREACHING FFGS ACROSS NORTHEAST OH, NORTHWEST PA, WITH WESTERN NY
SHOWING >70% CHANCE OF EXCEEDING FFGS.  AREAS OF SOUTHWEST PA AND
WV COULD SEE DELAYED ACTIVITY, HAVING POTENTIAL ISSUES BETWEEN 23Z
AND 04Z.  RAINFALL RATES UP TO 1.5" AN HOUR ARE EXPECTED
CONSIDERING THE AVAILABLE MOISTURE, WITH LOCAL AMOUNTS OF 2-4"
POSSIBLE WHERE CELLS MERGE, WHICH WOULD EXCEED FFGS.  FLASH
FLOODING IS CONSIDERED POSSIBLE.

ROTH

ATTN...WFO...BGM...BUF...CTP...LWX...PBZ...RLX...CLE...ILN...

ATTN...RFC...MARFC...NERFC...OHRFC...

LAT...LON   43517630 42667700 41717837 40217898 38997936 38208082
            38158211 38348306 38348307 38628339 39658230 40888148
            40888148 41618146 41848118 42218002 42847895 43307914
            43497820 43387710 43517630