MESOSCALE PRECIPITATION DISCUSSION 0707
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
747 PM EDT MON SEP 26 2016
 
AREAS AFFECTED...WESTERN AND CENTRAL NC 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 262345Z - 270345Z
 
SUMMARY...CONVECTION TRAINING OVER AREAS WITH LOWER FLASH FLOOD
GUIDANCE VALUES COULD RESULT IN AN ISOLATED FLASH FLOOD THREAT
THROUGH THE EVENING HOURS. 

DISCUSSION...A LINE OF CONVECTION FORMING IN THE WARM SECTOR AHEAD
OF A COLD FRONT OVER EASTERN TN HAS TAPPED 500-1000 J/KG OF
MLCAPE...IN AN AXIS OF 1.75 INCH PRECIPITABLE WATER AIR. THE
SOUTHERN EDGE OF THE LINE HAS STARTED SLOWING AND STRENGTHENING
OVER SOUTHWEST NC...AND THE KRAH RADAR HAS INDICATED HOURLY
RAINFALL RATES NEAR 1.50 INCHES OVER WESTERN FORSYTH COUNTY
RECENTLY.

THE CONVECTION IS ABOUT TO TRACK OVER AN AREAS WHERE ONE HOUR
FLASH FLOOD GUIDANCE VALUES ARE AS LOW AS 1.50 INCHES. RADAR
TRENDS SUGGEST THAT THE TRAINING CONVECTION COULD CROSS THESE
AREAS...WHICH WOULD RESULT IN A LOCALLY ENHANCED FLASH FLOOD
THREAT. 

THE LATEST RAP SUGGESTS THAT THE INSTABILITY (WITH MUCAPE VALUES
BETWEEN 500-1000 J/KG) COULD REMAIN IN PLACE AHEAD OF THE FRONT
THROUGH ABOUT 03Z...BEFORE IT WEAKENS. THIS COULD BE SUFFICIENT TO
ALLOW THE CONVECTION PRODUCE HOURLY RAINFALL RATES NEAR 1.50
INCHES...ESPECIALLY WHERE THE CONVECTION ON THE LINES HANGS UP.

THE LATEST HRRR IS THE MOST ROBUST PIECE OF HIGH RESOLUTION
GUIDANCE ACROSS CENTRAL NC...SHOWING A LOCAL 2-4 INCH MAXIMUM
(THOUGH ITS QPF BULLSEYE MAY END UP BEING TOO FAR NORTH...BASED ON
RADAR TRENDS. TRAINING COULD RESULT IN LOCAL MAXIMA CLOSE TO THESE
VALUES...BUT THE CORRIDOR OF THE FLASH FLOOD THREAT COULD END UP
BEING FAIRLY NARROW. FOR THIS REASON... FLASH FLOODING IS ONLY
CONSIDERED POSSIBLE. 

HAYES

ATTN...WFO...CAE...GSP...RAH...RNK...

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

LAT...LON   36537876 36117848 35757863 35048022 34958067 
            34948085 34998152 35058183 35168207 35318210 
            35538203 35898154 36158098 36288072