MESOSCALE PRECIPITATION DISCUSSION 0490
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1002 AM EDT FRI JUL 20 2018

AREAS AFFECTED...SE IN...NRN KY...SW OH

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 201402Z - 201902Z

SUMMARY...FLASH FLOODING APPEARS INCREASINGLY LIKELY THIS MORNING
IN NORTHERN KY AND POSSIBLY ADJACENT IN/OH AS SYNOPTIC FORCING
INCREASES AND BECOMES LOCALLY FOCUSED.

DISCUSSION...PER SURFACE OBSERVATIONS AND RADAR LOOPS NEARING
14Z...A COLD POOL WAS BECOMING ESTABLISHED AND AN MCV WAS EVIDENT
NEAR LEXINGTON KY...THE MCV HAVING ORIGINATED WITH A LONG LIVED
MCS THAT HAD NOW MERGED WITH CONVECTION FORMING IN A BROADER
REGION OF WARM ADVECTION.

THE WARM ADVECTION WAS OCCURRING ALONG AND DOWNWIND FROM THE
INSTABILITY GRADIENT AS A WARM SECTOR SOUGHT TO BECOME ESTABLISHED
AHEAD OF A 2.0 STANDARD DEVIATION UPPER LOW DIGGING THROUGH THE
MIDWEST. CONTINUED HEIGHT FALLS AHEAD OF THIS FEATURE...AND
ASSOCIATED LOW LEVEL RESPONSE...WILL MAINTAIN 20-30 KT LOW LEVEL
INFLOW INTO THE COLD POOL/MCV REGION...STRONG INFLOW BY SUMMER
STANDARDS. UPSTREAM SOUNDINGS AND THE SPC MESOANALYSIS INDICATE
STEEP LOW TO MID LEVEL LAPSE RATES SUPPORTING A CONTINUED FEED OF
UNSTABLE AIR INTO THE BACK SIDE OF THE MCV...AND LIKELY SUPPORTING
REDEVELOPMENT OF NEW CONVECTION ALONG STORM FLANKS...RESULTING IN
TRAINING.

CELL MOTIONS ARE OF CONCERN...AS CORFIDI DOWNWIND PROPAGATION IS
ALIGNED WITH THE MEAN 0-6KM WIND IN THIS CASE...AND PROPAGATION
INTO THE INFLOW WOULD YIELD CORFIDI BACK MOTION OF ZERO TO 5 OR 10
KNOTS. COUPLE THIS SETUP WITH A SUPPORTIVE MODEL SIGNAL OF SPOTTY
3-5 INCH RAINFALL THROUGH 19Z...AND FLASH FLOODING WOULD APPEAR
LIKELY...ESPECIALLY NEAR THE ONGOING LINE OF CONVECTION AT 14Z
NEAR LEXINGTON. ELSEWHERE IT REMAINS TO BE SEEN...BUT HEAVY SHORT
TERM RATES OVER 1.50 INCHES PER HOUR ARE POSSIBLE FARTHER
EAST...AND OTHER CLUSTERS OF STORMS MAY FORM BACK TO THE NORTH
TOWARD CINCINNATI OVER TIME AS THE WARM SECTOR CONTINUES TO EXPAND.

BURKE

ATTN...WFO...ILN...JKL...LMK...RLX...

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

LAT...LON   39388455 39038376 39278301 39058240 38388234
            37858294 37678378 37698464 38228550 39038537