MESOSCALE PRECIPITATION DISCUSSION 0323
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
145 PM EDT WED JUN 14 2017

AREAS AFFECTED...SOUTHERN IN/OH BORDER & EASTERN PORTIONS OF KY

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

VALID 141744Z - 142144Z

SUMMARY...SHOWERS AND THUNDERSTORMS HAVE SHOWED RENEWED VIGOR AS
INSTABILITY INCREASES ACROSS THE REGION.  HOURLY RAIN RATES UP TO
2.5", AND LOCAL AMOUNTS TO 4", ARE EXPECTED.

DISCUSSION...MORNING SHOWERS AND THUNDERSTORMS HAVE LAID OUT AN
OUTFLOW BOUNDARY EXTENDING ACROSS EASTERN KY AND SOUTHEAST IN
WHICH HAS BEEN SLOWLY EDGING WESTWARD.  MEANWHILE, A WEAK THERMAL
BOUNDARY IS MOVING INTO THE AREA FROM THE WEST WHICH IS LEADING TO
THE INSTABILITY GRADIENT TO BETTER ALIGN WITH THE OUTFLOW
BOUNDARY.  CLOUD STREETS ARE EVIDENT ON RECENT VISIBLE IMAGERY
FEEDING TOWARDS THESE BOUNDARIES.  ALOFT, AN MCV FROM OVERNIGHT
CONVECTION IS PASSING EASTWARD THROUGH NORTHEAST IN.  PRECIPITABLE
WATER VALUES ARE NEAR 1.75".  INFLOW AT 850 HPA REMAINS 15-20 KTS
(SLIGHTLY STRONGER THAN THE MEAN 850-400 HPA WIND) AND IS MOST
CONVERGENT INTO THE OH/IN/KY BORDER JUNCTION AT THIS TIME. 
EFFECTIVE BULK SHEAR IS BELOW 25 KTS.

THUNDERSTORMS HAVE SHOWN OCCASIONAL TRAINING/BACKBUILDING
TENDENCIES, WHICH MAY CONTINUE.  THE 00Z AND 12Z MESOSCALE
GUIDANCE ARE STARTING OFF AT A DISADVANTAGE IN THAT THE ONGOING
ACTIVITY WAS EXPECTED TO BE DEVELOPING AT THIS TIME, SO THE
MODEL-ADVERTISED PATTERNS AND AMOUNTS ARE PROBABLY TOO LOW. 
BELIEVE THE 12Z SPCWRF HAS THE BEST IDEA AT THE MOMENT.  AS THE
MCV MOVES FARTHER AFIELD, DIVERGENCE ALOFT ACROSS THE REGION
SHOULD WEAKEN SOMEWHAT WHICH COULD LEAD TO LESS ORGANIZATION WITH
TIME.  OFFSETTING THIS IS THE INCREASING INSTABILITY, AS MLCAPES
ARE 1000-2500 J/KG UPSTREAM WHICH COULD BUILD ANOTHER 500+ J/KG
OVER THE NEXT SEVERAL HOURS.  ANOTHER COMPLICATING FACTOR IS NEW
CONVECTION ACROSS NORTH-CENTRAL IL AND WESTERN IN WHICH COULD
MERGE INTO THIS ACTIVITY.  HOURLY RAIN RATES UP TO 2.5" WITH LOCAL
AMOUNTS UP TO 4" ARE CONSIDERED POSSIBLE.  CONSIDERING SATURATING
SOILS FROM YESTERDAY AND THIS MORNING'S RAINFALL, FLASH FLOODING
IS A CONCERN.

ROTH

ATTN...WFO...ILN...IND...JKL...LMK...MRX...OHX...RLX...

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

LAT...LON   40378624 39938442 38248307 36708327 36198385
            36048407 36428479 38628603