MESOSCALE PRECIPITATION DISCUSSION 0485
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1131 AM EDT THU JUL 13 2017

AREAS AFFECTED...SRN OH INTO FAR NWRN WV

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

VALID 131530Z - 131845Z

SUMMARY...A FLASH FLOOD THREAT WILL CONTINUE FOR AT LEAST ANOTHER
2-3 HOURS ACROSS SRN OH AND FAR NWRN WV. SCATTERED RUNOFF ISSUES
ARE EXPECTED AND RAINFALL RATES COULD EXCEED 2 IN/HR WHERE IDEAL
TRAINING DEVELOPS.

DISCUSSION...KILN AND KRLX RADAR IMAGERY SHOWED A REGION OF
CONVECTION OVER S-CNTRL OH WITH RADAR ESTIMATED RAIN RATES OF 1-2
IN/HR BUT AT LEAST ONE OBSERVATION IN NRN CLERMONT COUNTY ENDING
14Z REPORTED 1.65 INCHES IN 30 MINUTES. TRENDS IN EXPERIMENTAL
GOES 16 INFRARED IMAGERY SHOWED 50-75 MILE WIDE REGIONS OF RAPID
CLOUD TOP COOLING FOLLOWED BY WARMING. THIS RATHER DISORGANIZED
NATURE HAS BEEN OCCURRING WITHIN A REGION OF LOW LEVEL CONFLUENCE
ALONG THE SOUTHWESTERN TAIL END OF AN MCV WHICH WAS TRACKING EAST
INTO WRN NY AT 15Z. FLOW ALOFT WAS ALSO FAIRLY DIFFLUENT...CAUGHT
BETWEEN A 50-90 KT ZONALLY ORIENTED JET TO THE NORTH ACROSS THE
GREAT LAKES AND AN ELONGATED UPPER LEVEL RIDGE CENTERED TO THE
SOUTHWEST OVER THE LOWER OH VALLEY.

THE UPPER RIDGE IS FORECAST TO ELONGATE EASTWARD OVER THE NEXT 3-6
HOURS...REDUCING DIFFLUENT FLOW OVER SRN OH THROUGH 21Z. LOW LEVEL
CONFLUENCE IS ALSO EXPECTED TO WEAKEN SHORTLY...HOWEVER...THE AREA
WILL REMAIN VERY MOIST WITH PRECIPITABLE WATER VALUES OVER 2
INCHES IN A FEW LOCATIONS AND MORE THAN SUFFICIENT INSTABILITY.

SOME UNCERTAINTY IS PRESENT IN THE EXACT END TIME OF THE IMMEDIATE
FLASH FLOOD THREAT GIVEN POOR HANDLING BY RECENT CAM GUIDANCE AND
RECENT RUNS OF THE HRRR WHICH HAVE DISSIPATED CONVECTION TOO
EARLY. AT LEAST ANOTHER 2-3 HOURS OF AN ELEVATED FLASH FLOOD IS
EXPECTED ACROSS THE REGION...BEFORE EXPECTED WEAKENING...BUT
TRENDS WILL BE MONITORED FOR CHANGES.

OTTO

ATTN...WFO...CLE...ILN...PBZ...RLX...

ATTN...RFC...OHRFC...

LAT...LON   40488285 40458209 40318121 39868079 39368110
            38828231 38788374 38978457 39558467 40238383