MESOSCALE PRECIPITATION DISCUSSION 0538
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1125 PM EDT SAT JUL 22 2017

AREAS AFFECTED...SRN IL...SRN IN...SRN OH...NRN KY

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

VALID 230317Z - 230800Z

SUMMARY...TRAINING POTENTIAL WILL EXIST FOR THE NEXT FEW HOURS
WITH 1-2 IN/HR RAINFALL RATES EXPECTED FROM SRN IL/IN/OH INTO NRN
KY. LOCAL 2-3 INCH TOTALS ARE FORECAST.

DISCUSSION...TRENDS OVER THE PAST 1-2 HOURS HAVE SHOWN A UPTICK IN
CONVECTIVE COVERAGE NEAR AN ELONGATED OUTFLOW BOUNDARY EXTENDING
EWD FROM SRN IL INTO CNTRL WV. THE SPC MESOANALYSIS PAGE INDICATED
A RELATIVE MAX IN MLCAPE NEAR THE OUTFLOW BOUNDARY AT 02Z RANGING
FROM 1500-2500 J/KG. THE ENVIRONMENT WAS ALSO VERY RICH IN
MOISTURE WITH RECENT GPS PRECIPITABLE WATER VALUES IN THE VICINITY
OF THE OUTFLOW BOUNDARY RANGING FROM 1.75 TO 2.25 INCHES. 20-30 KT
OF WSWLY 850 MB FLOW WAS OVERRUNNING THE OUTFLOW
BOUNDARY...LEADING TO A BROKEN LINE OF CONVECTION WITH MEAN STORM
MOTIONS TRACKING PARALLEL TO THE BOUNDARY.

DUAL-POL DERIVED RAINFALL RATES HAVE BEEN MAXIMIZING BETWEEN 1-2
IN/HR WHERE CELL TRAINING BECOMES ESTABLISHED. WHILE THE DURATION
OF TRAINING HAS BEEN SHORT LIVED UP TIL NOW AND THE COVERAGE
RATHER SCATTERED ACROSS THE OHIO VALLEY...A SLIGHT INCREASE IN 850
MB WIND SPEEDS OVER THE NEXT 2-4 HOURS MAY ALLOW FOR INCREASED
TRAINING AND FLASH FLOOD POTENTIAL.

WHILE THIS REGION HAS BEEN RELATIVELY DRY OVER THE PAST WEEK...AND
FLASH FLOOD GUIDANCE IS ONLY LOWERED ACROSS NORTHERN PORTIONS OF
THE MPD THREAT AREA...TRAINING OF 1-2 IN/HR RAIN RATES MAY EXCEED
FLASH FLOOD GUIDANCE IN A FEW AREAS THROUGH 08Z LEADING TO SOME
SCATTERED FLASH FLOODING.

OTTO

ATTN...WFO...ILN...ILX...IND...JKL...LMK...LSX...PAH...RLX...

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

LAT...LON   39778748 39488433 38818263 38098296 37818354
            37968583 38418866 39368888