MESOSCALE PRECIPITATION DISCUSSION 0873
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1147 PM EDT SAT OCT 07 2017

AREAS AFFECTED...KENTUCKY...SOUTHWEST OHIO

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

VALID 080346Z - 080930Z

SUMMARY...A PLUME OF TROPICAL MOISTURE SITUATED ALONG A STALLING
FRONT WILL PROVIDE THE FOCUS FOR SLOW-MOVING AND TRAINING
CONVECTION. HEAVY RAINFALL IS LIKELY AND RATES UP TO 3 IN/HR WILL
BE POSSIBLE IN LOCALIZED AREAS. THIS WILL INCREASINGLY POSE A
FLASH FLOODING THREAT...PARTICULARLY OVER PORTIONS OF KENTUCKY.

DISCUSSION...CONVECTION IS ONGOING AT 0330Z ALONG A COLD FRONT
THAT EXTENDS FROM WESTERN OHIO INTO THE OHIO-RIVER-ADJACENT
PORTIONS OF KENTUCKY. STRONGER UPDRAFTS IN THE 01-02Z TIME FRAME
WERE MORE VIGOROUS...WITH EXPERIMENTAL GOES-16 IR CLOUD TOP
TEMPERATURES AS COLD AS -60C. HOWEVER THESE COLDER CLOUD TOPS HAVE
SINCE WANED...AND LIGHTNING ACTIVITY HAS BEEN REDUCED. THIS TREND
IS LIKELY TO CONTINUE INTO THE NIGHT AS THE CAPE PROFILE IN INFLOW
REGIONS BECOMES INCREASINGLY NARROW WITH A SATURATED COLUMN. IN
OTHER WORDS...THE FORECAST SOUNDINGS IN THE REGION TRANSITION MORE
MARKEDLY TO A CLASSIC HEAVY RAIN PROFILE OVER THE NEXT FEW HOURS.

DESPITE THAT...THERE HAVE ALREADY BEEN SOME SIGNIFICANT RAINFALL
RATES OBSERVED WHERE CELL TRAINING HAS BEEN OCCURRING. A KENTUCKY
MESONET SITE NEAR HARDINSBURG IN BRECKINRIDGE CO OBSERVED 1.3
INCHES OF RAIN IN 30 MINUTES...AND DUAL POL AND MRMS RAINFALL
ESTIMATES HAVE BEEN LOCALLY AS HIGH AS 3 IN/HR. THIS SHOULD
CONTINUE IN THE TROPICAL ENVIRONMENT...WITH A NARROW CAPE PROFILE
AND PRECIPITABLE WATER VALUES AROUND 2 INCHES. WHERE THE HIGHER
RATES CAN PERSIST FOR AN HOUR OR MORE...FLASH FLOODING WOULD BE
LIKELY TO DEVELOP. ALTHOUGH THE REGION HAS BEEN DRY OVER THE PAST
COUPLE WEEKS...THERE DOES APPEAR TO BE A NOTABLE HYDROLOGIC
RESPONSE (AS SIMULATED BY THE CREST MODEL; MOST PRONOUNCED THUS
FAR OVER MUHLENBERG AND OHIO COUNTIES) WHERE MRMS RAIN RATES HAVE
APPROACHED OR EXCEEDED 2 IN/HR. THIS APPEARS TO BE A GOOD
BASELINE...THAT THE MORE PROLIFIC RAIN RATES MAY BE ABLE TO
INITIATE SOME FLOODING...WHICH WOULD BE EXACERBATED IF HEAVY
RAINFALL CAN PERSIST FOR 2+ HOURS AT THAT LOCATION.

THE COLD FRONT WILL BE STALLING WITH TIME...WITH THE MORE
SIGNIFICANT FORCING OVER A DEEPER LAYER LIKELY TO BE PROGRESSIVE
THROUGH PARTS OF SOUTHWEST OHIO AND NORTHEAST KENTUCKY. THROUGH
10Z...THIS MAY LIMIT THE AMOUNT OF TIME ANY ONE LOCATION IN THOSE
REGIONS RECEIVES HEAVY RAINFALL. HOWEVER...OVER WESTERN AND
CENTRAL KENTUCKY...THE FRONT WILL BEGIN TO STALL AND FORCING FOR
ASCENT WILL BECOME INCREASINGLY FOCUSED IN THE LOWEST 1KM OR SO.
WINDS IN THAT LAYER ARE ALSO FORECAST TO WEAKEN...SO AS CONVECTION
BECOMES SHALLOWER WITH WEAKENING INSTABILITY...IT SHOULD BECOME
INCREASINGLY TIED TO THE LOW-LEVEL FRONT WITH SLOWER CELL MOTIONS.
THESE PROCESSES WOULD LIKELY LEAD TO THE GREATEST FLASH FLOOD
THREAT THROUGH 10Z FOCUSED IN A CORRIDOR FROM NEAR CADIZ KY TO
NEAR LEXINGTON KY.

LAMERS

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

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

LAT...LON   39958351 39558274 39178286 38708296 38228269
            37878297 37508406 36998539 36798650 36748675
            36738782 36808847 37198843 37558765 37878696
            38528591 39128499 39758416