MESOSCALE PRECIPITATION DISCUSSION 0103
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1200 PM EDT SUN APR 15 2018

AREAS AFFECTED...WRN SC/NC/VA INTO SRN WV

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

VALID 151559Z - 152100Z

SUMMARY...FLASH FLOODING WILL BE POSSIBLE ACROSS PARTS OF WRN
SC...WRN NC...WRN VA INTO SRN WV WITH RAINFALL RATES OF 1-2 IN/HR
AND PERIODS OF TRAINING THROUGH 21Z. 6 HR RAINFALL TOTALS OF 3-5
INCHES WILL BE POSSIBLE WHERE IDEAL CELL TRAINING DEVELOPS.

DISCUSSION...REGIONAL RADAR IMAGERY THROUGH 15Z SHOWED A
NORTH-SOUTH ORIENTED AXIS OF RAINFALL WITH EMBEDDED CONVECTION
EXTENDING FROM WRN NC SOUTHWARD INTO E-CNTRL GA. AN MCV WAS
EMBEDDED WITHIN THIS LINE OVER N-CNTRL GA AS OF 15Z...TRACKING
TOWARD THE NORTH-NORTHEAST WITH THE KJGX VAD WIND PLOT SHOWING AN
INCREASE IN 850 WIND SPEED FROM 50 TO 65 KT AHEAD OF THE MESOSCALE
CIRCULATION. A FEW NARROW LINES OF HEAVY RAIN HAVE ALREADY BEEN
OBSERVED VIA KGSP DUAL POL RADAR NEAR THE WRN NC/SC BORDER WITH 1
HR ESTIMATED RAIN RATES IN THE 1-1.5 IN/HR RANGE...CONFIRMED BY
ONE OR TWO NEARBY LOCAL SURFACE OBSERVATIONS THROUGH 14Z. WHILE
THESE HARROW LINES OF HEAVY RAIN HAVE GENERALLY BEEN PROGRESSIVE
OFF TO THE EAST...THERE IS SOME CONCERN FOR SLOWING OVER THE NEXT
FEW HOURS OR AT LEAST FOR REPEATING ROUNDS OF HEAVY RAIN.

AS AN UPPER LEVEL TROUGH AXIS CURRENTLY OVER THE LOWER MS VALLEY
MOVES EASTWARD THIS AFTERNOON...ITS DEGREE OF NEGATIVE TILT WILL
INCREASE ALLOWING FOR INCREASING UPPER LEVEL DIFFLUENCE AND
DIVERGENCE OVER THE CNTRL/SRN APPALACHIANS INTO THE
PIEDMONT...WITHIN THE RIGHT ENTRANCE REGION OF A 110-130+ KT JET
CORE OVER THE OHIO VALLEY. ENHANCED LOW LEVEL FLOW AHEAD OF THE
MCV IS EXPECTED TO ALLOW FOR BETTER CHANCES FOR THE CONVECTIVE
LINE TO TRAIN ALONG AS SPEEDS EXCEED THE 0-6 KM MEAN FLOW...ALONG
WITH AN INCREASED UPSLOPE COMPONENT INTO THE UPSLOPE FAVORED
TERRAIN OF THE PIEDMONT AND APPALACHIANS.

WHILE INSTABILITY IS ONLY EXPECTED TO INCREASE MARGINALLY INTO THE
AFTERNOON...WITH 250-750+ J/KG MUCAPE FORECAST BY THE RAP THROUGH
21Z...THE DEGREE OF MOISTURE ALREADY IN PLACE HAS PROVED TO BE
SUFFICIENT TO SUSTAIN RAIN RATES IN EXCESS OF 1 IN/HR SO ANY
INCREASES TO CAPE SHOULD ONLY ENHANCE RAINFALL INTENSITY.
LOCALIZED 3-5 INCH TOTALS ARE EXPECTED WHERE IDEAL CELL TRAINING
DEVELOPS.

OTTO

ATTN...WFO...CAE...GSP...MRX...RAH...RLX...RNK...

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

LAT...LON   37788106 37638048 37048026 36118046 35208094
            34118181 34298268 35418274 36738216 37328175