MESOSCALE PRECIPITATION DISCUSSION 0782
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
220 AM EDT TUE SEP 05 2017

AREAS AFFECTED...SOUTHERN OH...NORTHERN WV

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

VALID 050620Z - 051000Z

SUMMARY...SHORT TERM TRAINING COULD PRODUCE HOURLY RAINFALL RATES
NEAR 2.00 INCHES... WHICH IN TURN MAY PRODUCE A FLASH FLOOD THREAT
EARLY THIS MORNING.

DISCUSSION...THE GOES-16 CLEAN IR LOOP SHOWED THAT TOPS REMAIN
FAIRLY COLD WITH THE CONVECTION OVER WEST CENTRAL OH EARLY THIS
MORNING. THIS CLUSTER OF STORMS HAS PERSISTED IN AN AXIS OF
1000-1500 J/KG MLCAPE EXTENDING FROM WESTERN PA INTO WESTERN KY.
THE STEADY STATE CONVECTION IS RIDING ALONG A RIBBON OF 1.50/1.75
INCH PRECIPITABLE WATER AIR (PER THE MOST RECENT RAP ANALYSIS...AS
WELL AS THE BLENDED TPW PRODUCT).

THE KILN RADAR SHOWED HOURLY RAINFALL RATES BETWEEN 1.50 AND 2.00
INCHES...AND THIS IS BOLSTERED BY A SPOTTER REPORT OF 1.03 INCHES
OF RAIN IN 28 MINUTES NEAR LEBANON OH. WHILE THE CONVECTION
CONTINUES TO MOVE SLOWLY SOUTHEAST AHEAD OF THE COLD FRONT...
CELLS WITHIN THE CLUSTER ARE MOVING EAST... INCREASING THE
POTENTIAL FOR SHORT TERM TRAINING.

THE MOST RECENT HRRR SHOWED LOCAL 2.00/2.50 INCH RAINFALL AMOUNTS
WITH THE CONVECTION AS IT CROSSES SOUTHERN OH AND ENTERS NORTHERN
WV AFTER 0730Z. BASED ON WHAT HAS OCCURRED IN THIS AIRMASS THUS
FAR...THOSE AMOUNTS SEEM PLAUSIBLE...ESPECIALLY WHERE SHORT TERM
TRAINING OCCURS. IT SHOULD BE NOTED THAT THE MOST RECENT HRRR (AS
WELL AS MUCH OF THE AVAILABLE HIGH RESOLUTION GUIDANCE) IS AN HOUR
OR TWO SLOWER THAN REALITY.

ONE HOUR FLASH FLOOD GUIDANCE VALUES ACROSS PORTIONS OF SOUTHEAST
OH AND NORTHERN WV DROP AS LOW AS AN INCH (WITH THE LOWEST VALUES
OVER NORTHERN WV). AS THE CONVECTION ENTERS THE AREAS OF LOWER
FLASH FLOOD GUIDANCE...THE FLASH FLOOD THREAT INCREASES.

HAYES

ATTN...WFO...ILN...JKL...PBZ...RLX...

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

LAT...LON   40028046 39537981 38957998 38528064 38348250
            38518381 38638409 38628409 39118454 39748392
            40008182