MESOSCALE PRECIPITATION DISCUSSION 0025
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1056 AM EDT FRI APR 03 2015
 
AREAS AFFECTED...KY AND SOUTHWEST WV 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 031455Z - 032055Z
 
SUMMARY...AN MCV, DAYTIME HEATING, AND A PAIR OF SURFACE
BOUNDARIES WILL COMBINE FORCES WITH AVAILABLE MOISTURE AND
BUILDING INSTABILITY AFTER 16Z TO LEAD TO FLASH FLOODING WITHIN AN
AREA OF SATURATED SOILS.

DISCUSSION...A WEAKENING MESOSCALE CONVECTIVE SYSTEM HAS BEEN
MOVING BRISKLY EASTWARD ACROSS SOUTHWEST KY.  THE ENVIRONMENT IN
THE REGION IS SATURATED PER AREA SOUNDINGS, WITH WET BULB ZEROES
NEAR 9000 FT.  PRECIPITABLE WATER VALUES OF 1.25-1.5" PERSIST,
WHICH ARE OVER TWO SIGMAS ABOVE AVERAGE FOR EARLY APRIL.  INFLOW
AT 850 HPA IS 45-55 KTS INTO THE REGION, NEAR THE MAGNITUDE OF THE
850-400 HPA MEAN WIND.  THE BULK SHEAR ACROSS THE REGION IS 50-60
KTS, MORE THAN SUFFICIENT FOR ORGANIZED CONVECTION/SUPERCELLS. 
WINDS ARE NEARLY UNIDIRECTIONAL WITH HEIGHT, WITH PROPAGATION
VECTORS NEARLY ALIGNED WITH THE MEAN WIND.  MUCH OF CENTRAL AND
NORTHERN KY IS SATURATED, WITH THREE HOURLY FFGS NEAR OR BELOW
1.5".

THE EXPECTATION IS FOR INSTABILITY/CAPE VALUES TO BUILD BACK TO
1000+ J/KG AFTER 16Z PER RECENT RAP RUNS, WITH THE AREA OF 500+
J/KG SPREADING EASTWARD ACROSS THE WIDTH OF SOUTHERN KY/NORTHERN
TN WITH TIME.  THIS MAGNITUDE OF INSTABILITY SHOULD BE ENOUGH FOR
THE WET MULTICELL ENVIRONMENT, PER THE SATURATED SOUNDING PROFILES
SEEN THIS MORNING.  THE OUTFLOW BOUNDARY WILL TRY TO RETURN
NORTHWARD, BUT SHOULD NOT MAKE MUCH HEADWAY TODAY EXCEPT ACROSS
EASTERN KY AHEAD OF AN MCV LEFT OVER FROM THE CURRENT MCS ACROSS
SOUTHWEST KY.  A COLD FRONT WILL SWEEP THROUGH THE AREA FROM WEST
TO EAST, ACTING AS THE BACK EDGE FOR THE HEAVY RAINFALL THREAT. 
HOURLY RAINFALL RATES OF 1.5" ARE POSSIBLE, WITH THE MESOSCALE
GUIDANCE SUGGESTING LOCAL AMOUNTS OF 2"+ NEAR THIS REGION OVER THE
NEXT SEVERAL HOURS. THIS MAGNITUDE OF RAIN WOULD EASILY EXCEED
FFGS.  CELL TRAINING WOULD BE THE MAIN FLASH FLOOD THREAT.  FLASH
FLOODING IS CONSIDERED LIKELY AFTER 16Z.  THE SITUATION WILL BE
MONITORED IN CASE AN ADDITIONAL DISCUSSION IS NEEDED MID-AFTERNOON
TO COVER THROUGH 00Z.

ROTH

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

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

LAT...LON   38678180 37688130 37248200 36698385 36488735 
            36548944 37218813 38478474