MESOSCALE PRECIPITATION DISCUSSION 0236
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
345 PM EDT FRI MAY 19 2017

AREAS AFFECTED...SOUTHERN IN & SOUTHERN OH

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

VALID 191945Z - 200145Z

SUMMARY...THUNDERSTORMS ARE BEGINNING TO EXPAND IN COVERAGE IN THE
WARM ADVECTION PATTERN AHEAD OF A MESOSCALE WAVE.  HOURLY RAIN
RATES UP TO 2" WITH LOCAL AMOUNTS OF 2-4" COULD LEAD TO HEAVY RAIN
ISSUES.

DISCUSSION...A MESOSCALE WAVE INDUCED BY EARLIER CONVECTION ALONG
AN OLD OUTFLOW BOUNDARY COUPLED WITH A WEAK SHORTWAVE MOVING
ACROSS CENTRAL IN APPEAR TO BE ALLOWING CONVECTIVE EXPANSION
ACROSS SOUTHEAST IN AT THE PRESENT TIME.  PRECIPITABLE WATER
VALUES OF ~1.5" EXIST HERE.  CONVERGENT 850 HPA INFLOW OF 25-30
KTS IS IMPORTING MLCAPES OF 2000+ J/KG OUT OF WESTERN KY.  BULK
SHEAR OF ~25 KTS SHOULD ALLOW FOR CONVECTIVE ORGANIZATION, IN THIS
CASE IN THE FORM OF SHORT TRAINING BANDS AS THE FLOW IS NEARLY
UNIDIRECTIONAL WITH HEIGHT.

THE 12Z GFS-BASED GALVEZ-DAVISON INSTABILITY INDEX SHOWS A
FAVORABLE ENVIRONMENT FOR EXPANDING CONVECTION AS VALUES BREACH 30
BY 00Z.  THE 12Z WRF NSSL, 12Z NAM CONEST, AND 12Z CANADIAN
REGIONAL MODEL HAVE A SIGNAL IN THIS REGION, THOUGH AS USUAL THEY
COULD BE A BIT TOO FAR TO THE NORTH.  HOURLY RAIN RATES UP TO 2",
ALONG WITH LOCAL AMOUNTS OF 2-4", COULD LEAD TO HEAVY RAIN ISSUES
IN AN AREA WITH MODEST FLASH FLOOD GUIDANCE VALUES.

ROTH

ATTN...WFO...CLE...ILN...IND...LMK...PBZ...RLX...

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

LAT...LON   40438227 39978092 38788231 38418432 38458670
            39438560 40368436