MESOSCALE PRECIPITATION DISCUSSION 0142...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
233 PM EDT MON APR 24 2017

CORRECTED FOR RESENT TEXT AS OLD FILE

AREAS AFFECTED...SOUTH CENTRAL & SOUTHEASTERN NC...EASTERN SC

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

VALID 241745Z - 242345Z

SUMMARY...SLOW MOVING ONSHORE BANDS WITH TRAINING CONVECTIVE
ELEMENTS CONTINUE TO POSE FLOODING CONCERN.

DISCUSSION...DEEP UPPER LOW CONTINUING TO DRIFT ESE ACROSS CENTRAL
GA WITH NEARLY 120 DEGREES OF DIFFLUENCE ACROSS SC/NC CONTINUING
TO AID BROAD UVV ENVIRONMENT.  AT THE SURFACE A WEAK SURFACE 1004
MB REFLECTION JUST NORTH OF HILTON HEAD ISLAND WILL CONTINUE TO
HUG THE SC COAST ALONG A WARM FRONT THAT REMAINS NEARLY LOCKED TO
THE COAST FROM JUST NORTH OF CHS TO MYR TO NJM INTO THE OUTER
BANKS.  MAIN N-S ORIENTED BAND OF CONVECTION OVER E SC THAT HAD
BEEN FORCED BY LOW LEVEL CONFLUENCE AND ISENTROPIC ASCENT IS
CURRENTLY FADING HAVING EXHAUSTED MUCH OF THE LOCAL INSTABILITY IN
FAVOR OF UPSTREAM STRONGER HEIGHT FALLS AT LEADING EDGE OF CAA
DEPICTED IN GOES-16 WHICH HAVE LEAD TO AN INCREASE OF MLCAPE TO
1000 J/KG AROUND CHS WHICH IS LIFTED ISENTROPICALLY OVER THE FRONT
TO INTENSIFY THE LINE WITH 1.25-1.75"/HR RATES LIKELY.
 
ADDITIONALLY...LOW LEVEL FLOW HAS SLACKED A BIT ACROSS E SC/SE NC
IN THE SHORT-TERM AS CONVERGENCE BAND/MST SURGE EMANATING FROM THE
TROPICAL FEATURE SOUTHEAST IS ADVANCING TOWARD THE REGION SPARKING
ADDITIONAL SHOWERS ALONG THE WARM FRONT.  FLOW WILL CONTINUE TO
STRENGTHEN THROUGH THE EARLY AFTERNOON AS THE SFC GRADIENT
TIGHTENS WITH THE APPROACH OF THE SFC WAVE OUT OF THE TROPICAL
STREAM.  THIS WILL COME WITH AN INCREASE OF OVERALL MOISTURE WITH
TPWS INCREASING FROM 1.5 TO 1.75" TOWARD 21Z ALONG THE SC/NC
BORDER.  THIS WILL CORRESPOND WITH INCREASED RAINFALL EFFICIENCY
WITH RATES INCREASING FROM 1.5 TO 2.0"/HR AS WELL AS FOCUSED
ASCENT REORIENTING THE BAND FROM NW-SE TO MORE E-W THIS MAY BACK
THE LINE OVER AREAS THAT HAVE ALREADY BEEN AFFECTED OR WILL BE
AFFECTED IN THE NEXT FEW HOURS COMPOUNDING TOTALS WITH AN
ADDITIONAL 3-5" POSSIBLE NEAR ONGOING FLOODING CONDITIONS AS SUCH
FF REMAINS LIKELY HERE.  THIS IS SUPPORTED BY HI-RES CAMS
PARTICULARLY RECENT HRRR AND NAM CONEST AND 12Z GFS.  

FURTHER NORTHWEST TOWARD CHARLOTTE...WITH WARM FRONT LIKELY TO NOT
ADVANCE NW ACROSS NC...TRAINING THUNDERSTORMS NEARER THE COAST
WILL WEAKEN THOUGH MODERATE SHIELD PRECIPITATION WITH OCCASIONAL
EMBEDDED CONVECTION MAY LEAK OVER TOWARD THE CHARLOTTE METRO AREA
WHERE RAINFALL TOTALS MAY NOT BE AS GREAT AS FURTHER SOUTHEAST BUT
1-2.5" POSSIBLE OVER THE NEXT 6HRS MAY EXCEED THE ALREADY LOW FFG
IN THAT REGION KEEPING FF THREAT POSSIBLE THROUGH 00Z.

GALLINA

ATTN...WFO...CAE...CHS...GSP...ILM...RAH...

ATTN...RFC...SERFC...

LAT...LON   35627976 34827839 34317760 34157765 33747786
            33697819 33537868 33207895 32897938 32787976
            33118003 33548055 33908094 34228123 34868129
            35198118 35528083