MESOSCALE PRECIPITATION DISCUSSION 0266
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
540 PM EDT TUE MAY 23 2017

AREAS AFFECTED...SOUTHEAST GA...EASTERN SC

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

VALID 232140Z - 240100Z

SUMMARY...CONVECTION TRAINING IN A HIGH MOISTURE ENVIRONMENT AHEAD
OF A COLD FRONT COULD POSE A FLASH FLOOD THREAT INTO THE EVENING
HOURS.

DISCUSSION...REGIONAL RADARS ACROSS SOUTHERN GA INTO EASTERN SC
SHOWED CONVECTIVE ACTIVITY INCREASING AHEAD OF A WEAK COLD FRONT.
THE MOST RECENT EXPERIMENTAL GOES-16 IMAGES SHOWED SLOWLY COOLING
CLOUD TOPS OVER SOUTHEAST GA...WITH THE CONVECTION FORMING IN A
GRADIENT OF MLCAPE (WITH VALUES GENERALLY RANGING BETWEEN 500-1000
J/KG).

A 25 TO 35 KNOT LOW LEVEL FLOW (PER RECENT VWP ANALYSIS) CONTINUED
TO REPLENISH THE MOISTURE PLUME (WITH PRECIPITABLE WATER VALUES
NEAR 2.00 INCHES...AS SEEN ON THE MOST RECENT BLENDED TPW IMAGES).
HOURLY RAINFALL RATES HAVE TOPPED OUT NEAR 1.50 INCHES (BASED ON
THE MOST RECENT KJGX RADAR ESTIMATES)...WHICH IS BELOW THE ONE
HOURLY FLASH FLOOD GUIDANCE VALUES OVER SOUTHEAST GA.

THE HIGH RESOLUTION GUIDANCE IS SPLIT CONCERNING THE FLASH FLOOD
THREAT...WITH THE LATEST HRRR AND 12Z NSSL WRF THE MOST
AGGRESSIVE...INDICATING LOCAL 2.00 TO 4.00 INCH RAINFALL AMOUNTS
THROUGH 00Z ACROSS SOUTHEAST GA AND FAR EASTERN SC. THE LATEST RAP
INDICATES THAT THE MID LEVEL FLOW (850-300 MB) SHOULD REMAIN QUASI
UNIDIRECTIONAL...INCREASING THE POSSIBLY OF TRAINING...AND LOCALLY
HIGHER RAINFALL AMOUNTS.

THE LATEST HRRR SOIL MOISTURE PRODUCT SHOWED NEARLY SATURATED
GROUND OVER THIS AREA...ESPECIALLY OVER AREAS THAT RECEIVED HEAVY
RAINFALL IN THE PAST 24 HOURS. TRAINING CONVECTION OVER THIS AREA
REPRESENTS THE GREATEST THREAT FOR FLASH FLOODING INTO THE EVENING
HOURS.

HAYES

ATTN...WFO...CAE...CHS...ILM...JAX...

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

LAT...LON   33617969 33367929 31628166 31738209 31988217
            32288208 32538184 33508018