MESOSCALE PRECIPITATION DISCUSSION 0169
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
855 PM EDT FRI MAY 18 2018

AREAS AFFECTED...CENTRAL/NORTHERN KY...FAR SOUTHEAST
IN...SOUTHWEST OH

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

VALID 190055Z - 190500Z

SUMMARY...ADDITIONAL HEAVY RAIN IS EXPECTED TO CAUSE CONCERNS FOR
FLASH FLOODING THROUGH THE EVENING HOURS. IMPROVEMENT EXPECTED
TOWARD MIDNIGHT.

DISCUSSION...A BROAD UPPER TROUGH AND ASSOCIATED UPPER LOW OVER
THE MID MS VALLEY AND ADJACENT AREAS OF THE MID SOUTH CONTINUE TO
FOSTER AN ENVIRONMENT CONDUCIVE FOR BROKEN AREAS OF CONVECTION
OVER THE GREATER OH VALLEY REGION. IN FACT...THE LATEST GOES-16
CLEAN IR SATELLITE LOOP HAS BEEN SHOWING A PERSISTENCE OF COLD
CONVECTIVE TOPS OVER CENTRAL/NORTHERN KY AND ADJACENT AREAS OF FAR
SOUTHEAST IN CLOSE TO THE OH RIVER.

THE FLOW ALOFT IS BROADLY DIFFLUENT AND THERE REMAINS A POOL OF
WEAK TO MODERATE INSTABILITY FROM AFTERNOON DIURNAL HEATING WHICH
IS CONTRIBUTING TO AS MUCH AS 1500+ J/KG OF SBCAPE.
ADDITIONALLY...THERE IS BROAD SOUTHERLY FLOW OVERRUNNING A
QUASI-STATIONARY FRONT. PWATS ACROSS THE REGION REMAIN QUITE HIGH
WITH VALUES AS HIGH AS 1.7 TO 1.8 INCHES...WHICH COUPLED WITH THE
DEEPER COLD CONVECTIVE TOPS IS PRODUCING ENHANCED RAINFALL RATES
OF AS MUCH AS 2 INCHES/HR.

OVER THE NEXT FEW HOURS...CONVECTION IS EXPECTED TO PERSIST...WITH
SOME GRADUAL DECREASE IN COVERAGE BY LATE EVENING AS SURFACE-BASED
INSTABILITY BECOMES INCREASINGLY EXHAUSTED. ADDITIONAL RAINFALL
AMOUNTS LOCALLY OF AS MUCH AS 3 TO 4 INCHES CAN BE EXPECTED...AND
GIVEN THE WET ANTECEDENT CONDITIONS...THERE WILL BE CONCERNS FOR
ENHANCED RUNOFF. THE GREATEST POTENTIAL OVER THE NEXT COUPLE OF
HOURS WILL BE AROUND THE GREATER LOUISVILLE/CINCINATTI
METROPOLITAN AREA WHERE THESE URBANIZED ENVIRONMENTS WILL TEND TO
SEE MORE FOCUSED RUNOFF CONCERNS AND FLASH FLOODING.

ORRISON

ATTN...WFO...ILN...IND...JKL...LMK...

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

LAT...LON   39978478 39768431 39288394 38538351 37528330
            37248346 37238380 37848458 38558515 39238549
            39858540