MESOSCALE PRECIPITATION DISCUSSION 0269
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
320 PM EDT WED MAY 24 2017

AREAS AFFECTED...SC INTO CENTRAL NC

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

VALID 241920Z - 242320Z

SUMMARY...CONVECTION TRAINING ACROSS SC INTO PORTIONS OF CENTRAL
NC COULD RESULT IN A FLASH FLOOD THREAT THROUGH THE EARLY EVENING
HOURS.

DISCUSSION...REGIONAL RADARS SHOWED AN INCREASING AREA OF
CONVECTION OVER CENTRAL SC...WHERE THE EXPERIMENTAL GOES-16 CLEAN
IR LOOP SHOWED SLOWLY COOLING TOPS IN THE INCREASINGLY DIFLUENT
FLOW AHEAD OF A CLOSED MID LEVEL LOW OVER NORTHERN KY. THE
CONVECTION IS FORMING/STRENGTHENING IN AN AXIS OF 500-1000
J/KG...ON THE NORTHWEST EDGE OF A PRECIPITABLE WATER GRADIENT...
WITH THE BEST MOISTURE PLUME LOCATED OVER SOUTHEAST GA AND THE
COASTAL WATERS OF SC.

THE INCREASINGLY DIFLUENT FLOW SHOULD PROVIDE SUFFICIENT SYNOPTIC
SCALE ASCENT TO SUPPORT CONVECTION ACROSS CENTRAL SC INTO SOUTH
CENTRAL NC THROUGH 00Z. THE LATEST RAP SHOWED THAT THE INSTABILITY
MAY BECOME THE LIMITING FACTOR FOR MORE WIDESPREAD
CONVECTION...ESPECIALLY AFTER 23Z OR SO.

BEFORE THAT TIME...LOW LEVEL CONVERGENCE EAST OF THE TERRAIN
SHOULD SUPPORT TRAINING CONVECTION INTO THE LATE AFTERNOON HOURS.
MOST OF THE AVAILABLE HIGH RESOLUTION GUIDANCE IS TOO FAR
NORTHWEST WITH THE CURRENT CONVECTION...AND AN HOUR OR TWO SLOWER
THAN REALITY. BASED ON HOURLY RAINFALL RATES SHOWN ON THE KGSP
RADAR... THE 2.00 TO LOCAL 4.00 INCH RAINFALL AMOUNTS SHOWN BY THE
12Z NSSL WRF SEEM PLAUSIBLE.

THREE HOUR FLASH FLOOD GUIDANCE VALUES DROP OFF TO LESS THAN 1.50
INCHES OVER PORTIONS OF SOUTH CENTRAL NC...INCREASING THE
POTENTIAL FOR FLASH FLOODING. DIMINISHING INSTABILITY MAY RESULT
IN A GRADUAL DECREASE IN CONVECTION...AND FLASH FLOOD
POTENTIAL...AFTER 00Z.

HAYES

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

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

LAT...LON   35978003 35157940 33858003 33008106 33168176
            34148221 35488102