MESOSCALE PRECIPITATION DISCUSSION 0362
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1151 AM EDT TUE JUN 26 2018

AREAS AFFECTED...ERN KY AND TN...WRN VA AND NC...NWRN SC

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

VALID 261550Z - 262100Z

SUMMARY...SLOW-MOVING CONVECTIVE CELLS PRODUCING ISOLATED RAINFALL
RATES OF 1-2 IN/HR COULD RESULT IN LOCALIZED FLASH FLOODING
THROUGH 22Z.

DISCUSSION...SHOWERS AND THUNDERSTORMS ARE FOCUSING ALONG A
QUASI-STATIONARY FRONTAL BOUNDARY FROM ERN KY INTO SWRN VA LATE
THIS MORNING. RELATIVELY WEAK MID-LEVEL FLOW ALONG WITH NEARLY
PARALLEL FLOW AT THE LOWER LEVELS IS RESULTING IN SLOW CELL MOTION
WITH SOME BACKWARD PROPAGATION NOTED. INSTABILITY IS RELATIVELY
MODEST (MLCAPE OF 500-1000 J/KG ON LATEST MESOANALYSIS), AND WEAK
SHEAR IS RESULTING IN RATHER SLUGGISH ORGANIZATION PROCESS.
NONETHELESS, A VERY MOIST AIR MASS (PWATS OF 1.5-1.8 IN AND 850
HPA DEW POINTS OF 14-16 DEG C) IS RESULTING IN AT LEAST SOME
DEGREE OF ENHANCED INCREASED PRECIPITATION EFFICIENCY.

THE HRRR-EXPERIMENTAL SEEMS TO HAVE THE BEST HANDLE ON THE ONGOING
CONVECTION AT THE MOMENT, AND SHOWS A CONTINUED GRADUAL INCREASE
IN ORGANIZATION OVER THE NEXT FEW HOURS WITH AN EVENTUAL INCREASE
IN MOTION TOWARD THE SOUTHEAST, INTO WESTERN NORTH CAROLINA.
INCREASING INSTABILITY INTO THE AFTERNOON MAY BOOST POTENTIAL MAX
RAINFALL RATES SOMEWHAT, AND THE HRRR-TIME LAGGED ENSEMBLE
SUGGESTS INCREASING POTENTIAL FOR ISOLATED 2 IN/HR RAINFALL RATES
INTO THE AFTERNOON. FLASH FLOOD GUIDANCE IS HIGHER TOWARD THE
SOUTHERN/SOUTHEASTERN PORTION OF THE OUTLINED AREA, AND A GENERAL
INCREASE IN FORWARD MOTION OF CONVECTION SHOULD KEEP THE HEAVY
RAINFALL THREAT RELATIVELY LOCALIZED. NONETHELESS, THE POTENTIAL
FOR RELATIVELY HIGH RAINFALL RATES ALONG WITH SOME CELL
REDEVELOPMENT/PROPAGATION (CORFIDI VECTORS AROUND 5 KT) SUGGESTS
THE POTENTIAL FOR AT LEAST LOCALIZED FLASH FLOODING THROUGH THE
AFTERNOON, WITH ISOLATED 2-3 INCH RAINFALL TOTALS.

RYAN

ATTN...WFO...GSP...JKL...MRX...RLX...RNK...

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

LAT...LON   37548265 37168177 36488086 35588078 34958160
            35008249 35578331 36508373 36648375 37308343