MESOSCALE PRECIPITATION DISCUSSION 0177
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
307 PM EDT MON MAY 01 2017

AREAS AFFECTED...WESTERN PA...WESTERN NY

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 011859Z - 012200Z

SUMMARY...THUNDERSTORMS COULD PRODUCE LOCALIZED FLASH FLOODING AS
THEY MOVE THROUGH WESTERN PA AND WESTERN NY DURING THE NEXT FEW
HOURS.

DISCUSSION...THUNDERSTORMS ASSOCIATED WITH THE FRONTAL BAND MOVING
THROUGH WESTERN PA AND WESTERN NY COULD PRODUCE LOCALIZED FLASH
FLOODING DURING THE NEXT SEVERAL HOURS. THESE STORMS ARE MOVING
INTO A VERY MOIST AIR MASS WITH PRECIPITABLE WATER VALUES MAINLY
IN THE 1.50-1.75 INCH RANGE. SOUTHERLY FLOW AHEAD OF THE FRONT IN
THE 925-850 MB LAYER IS 35-50 KT. THE ENVIRONMENT IS MODESTLY
UNSTABLE WITH SPC MESOSCALE ANALYSES INDICATING CAPE VALUES
GENERALLY 500-1000 J/KG.

PBZ DUAL POL RADAR INDICATES HOURLY RAIN RATES OF LOCALLY 0.5-1.0"
OVER EASTERN OHIO WITH LOCAL RAINFALL ACCUMULATIONS EXCEEDING
1.5". SEVERAL HIRES MODELS - INCLUDING THE HRRR...ARW...AND RAP -
SUPPORT THE IDEA THAT THESE RAINFALL RATES WILL CONTINUE OR
INCREASE SLIGHTLY AS THE SYSTEM MOVES EAST INTO THE SOMEWHAT MORE
FAVORABLE ENVIRONMENT IN THE THREAT AREA. SOME TRAINING ALONG THE
SOUTH-NORTH ORIENTED PRECIPITATION LINE COULD LOCALLY BOOST
RAINFALL AMOUNTS.

RAINFALL TOTALS OF 1-2" ARE LIKELY ACROSS THIS REGION. WHILE THESE
ARE RATHER MODEST RAINFALL AMOUNTS...IT WILL OCCUR OVER A REGION
WHERE 3-HOUR FFG IS ALSO 1-2"...SO LOCALIZED FLASH FLOODING IS
POSSIBLE.

MCDONNAL

ATTN...WFO...BGM...BUF...CLE...CTP...PBZ...

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

LAT...LON   43387873 43277751 42577750 40627821 40007850
            39918016 41688013 42288000 42657963 43217903