MESOSCALE PRECIPITATION DISCUSSION 0062
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1209 AM EDT THU MAY 15 2014
 
AREAS AFFECTED...ERN GA...WRN SC...WRN NC 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 150408Z - 151008Z
 
SUMMARY...THUNDERSTORMS PRODUCING AT LEAST 1.5 INCH PER HOUR RATES
WILL TRAIN FOR AN EXTENDED PERIOD AS MID LEVEL STEERING WINDS
REMAIN ALIGNED WITH LOW LEVEL INFLOW. WITH DEEP MOISTURE ARRIVING
IT MAY ONLY TAKE 2 TO 3 HOURS FOR A GIVEN LOCATION TO MEET THE
RELATIVELY HIGH FLASH FLOOD GUIDANCE VALUES HERE.

DISCUSSION...FLASH FLOOD GUIDANCE VALUES WERE HIGH...ABOUT 3 TO 4
INCHES IN 3 HOURS...BUT RADAR TRENDS WERE WORRISOME AT 0345Z WITH
INCREASED ECHO INTENSITY AND SOUTH TO NORTH TRAINING. DEEP ASCENT
WILL BE SUSTAINED OVERNIGHT WITH LITTLE EASTWARD ADVANCEMENT OF
THE LARGE SCALE FEATURES. INSTABILITY WILL BE SUPPLIED BY LOW
LEVEL WINDS CHANNELING THROUGH SC AND SE GA...NOTING ONE OF THE
MORE UNSTABLE SOUNDINGS THIS EVENING WAS AT CHARLESTON SC. THE RAP
FORECASTS MODEST BUT SUFFICIENT CAPE TO PERSIST ALONG THE EASTERN
EDGE OF ONGOING THUNDERSTORMS IN GEORGIA...AND SPREADING INTO
SC/NC THROUGH 10Z. DEEP UNIDIRECTIONAL FLOW IN THE CLOUD LAYER
WILL PROMOTE TRAINING WHILE CORFIDI VECTORS SUGGEST VERY MINIMAL
EASTWARD PROPAGATION INTO THE INFLOW. THIS WAS ALREADY SEEN THIS
EVENING IN CENTRAL GA...AND RECENT HRRR RUNS SUGGEST THIS SCENARIO
WILL PERSIST SEVERAL HOURS. AT THE SAME TIME...TOTAL COLUMN
MOISTURE SHOULD OVERSPREAD WRN SC/NC...AND DESPITE WIDESPREAD
RAIN...THE SUSTAINED ASCENT WILL MAINTAIN MID LEVEL LAPSE RATES
SUFFICIENT FOR EMBEDDED CONVECTION. THE RESULT IS A FOCUSED HEAVY
RAIN THREAT.

INITIAL RADAR AND GAUGE OBSERVATIONS IN GA SUGGEST 1.5 INCH PER
HOUR RATES WILL BE COMMON...MEANING THE FLASH FLOOD GUIDANCE AT A
GIVEN LOCATION COULD BE BREACHED ONLY 2-3 HOURS AFTER ONSET.

BURKE

ATTN...WFO...RNK...CAE...GSP...MRX...FFC...

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

LAT...LON   32758377 33218393 33928402 34748398 35258378 35718306
            36398162 36398115 36008105 34318153 33408197 32668242
            32278295 32418351 32758377