Graphic for MPD #0757

MESOSCALE PRECIPITATION DISCUSSION 0757
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
956 PM EDT MON AUG 28 2017

AREAS AFFECTED...NORTHEAST SC INTO EASTERN NC

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

VALID 290200Z - 290800Z

SUMMARY...CONVECTION ASSOCIATED WITH POTENTIAL TROPICAL CYCLONE
TEN COMING ASHORE OVER NORTHEAST SC INTO EASTERN NC COULD PRODUCE
A FLASH FLOOD THREAT INTO THE EARLY MORNING HOURS.

DISCUSSION...THE GOES-16 CLEAN IR LOOP SHOWED DEEPENING CONVECTION
EAST OF POTENTIAL TROPICAL CYCLONE TEN...WITH THE COLDEST TOPS
WELL EAST OF KCHS. HOWEVER... TO THIS POINT...DRIER AIR ON THE
WESTERN SIDE OF THE LOW AND MID LEVEL SYSTEM HAS ERODED THE
CONVECTION AS IT APPROACHES THE SC/NC COASTS.

SOUTH OF A STATIONARY FRONT EXTENDING ALONG THE SC/NC COAST...THE
MOST RECENT RAP ANALYSIS SHOWED 500-1000 J/KG OF MLCAPE OFFSHORE.
CLOSER TO THE COAST (AND VERY CLOSE TO THE FRONTAL BOUNDARY)...THE
00Z CHS AND 00Z ILM SOUNDINGS SHOWED SBCAPE VALUES BELOW 500 J/KG.
THE MINIMAL  INSTABILITY HAS BEEN THE MAIN REASON THAT THE
CONVECTION HAS WEAKENED AS IT APPROACHES THE COAST. 

THERE IS STILL A MULTI HIGH RESOLUTION MODEL SIGNAL THAT SHOWS AN
INCREASING LOW LEVEL SOUTH SOUTHEAST FLOW (INCREASING TO NEAR 35
KNOTS AFTER 05Z ACROSS NORTHEAST SC AND EASTERN NC...PER THE MOST
RECENT RAP) TRANSPORTING DEEP MOISTURE AND INSTABILITY ALONG
COASTAL SECTIONS OF NORTHEAST SC AND EASTERN NC AS THE LOW LEVEL
BOUNDARY IS BODILY MOVED INLAND. MARGINAL INSTABILITY AND
PRECIPITABLE WATER VALUES BETWEEN 2.25/2.50 INCHES WILL POSE THE
THREAT FOR AT LEAST LOCALIZED FLASH FLOODING ACROSS THIS
AREA...MAINLY BETWEEN 05Z AND 08Z.

THE MOST RECENT HRRR SHOWED LOCAL 3.00 TO 5.00 INCHES OF RAINFALL
OVER FAR NORTHEAST SC AND MUCH EASTERN NC...AND THIS IS SUPPORTED
BY THE 12Z WRF ARW AND THE 12Z WRF NSSL SOLUTIONS. WHILE THREE
HOUR FLASH FLOOD GUIDANCE VALUES ARE GENERALLY ABOVE 3.00 INCHES
ALONG MUCH OF THE COAST...HIGH RAINFALL RATES WITH THE CONVECTION
POSE THE THREAT FOR AT LEAST LOCALIZED FLASH FLOODING.

SINCE THERE IS SOME SPREAD IN THE HIGH RESOLUTION MODEL GUIDANCE
AS TO WHETHER THE INSTABILITY PUSHES FAR ENOUGH INLAND THROUGH
08Z...FLASH FLOODING IS ONLY CONSIDER POSSIBLE INTO THE EARLY
MORNING HOURS.

HAYES

ATTN...WFO...ILM...MHX...

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

LAT...LON   35717645 35627539 34957606 34427721 33777832
            33257919 33957910


Last Updated: 956 PM EDT MON AUG 28 2017