MESOSCALE PRECIPITATION DISCUSSION 0507
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
314 AM EDT SUN JUL 22 2018

AREAS AFFECTED...CENTRAL NC

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

VALID 220713Z - 221013Z

SUMMARY...THUNDERSTORMS ARE BEGINNING TO TRAIN AHEAD OF A
MESOSCALE WAVE.  HOURLY RAIN TOTALS TO 2" WITH LOCAL AMOUNTS TO 4"
ARE POSSIBLE.

DISCUSSION...A CONVECTIVE SHORTWAVE IN SC AND AN ASSOCIATED
OUTFLOW BOUNDARY HAVE LED TO THE DEVELOPMENT OF A MESOSCALE WAVE
WEST OF LAURINBURG NC AND A CONVECTIVE BAND WITHIN ITS WARM AIR
ADVECTION PATTERN.  PRECIPITABLE WATER VALUES OF 1.5-1.9" EXIST IN
THIS AREA PER GPS DATA.  INFLOW AT 850 HPA IS CONVERGENT OUT OF
THE WEST-SOUTHWEST AT 20-25 KTS PER VAD WIND PROFILES, IMPORTING
MU CAPE VALUES OF 1000+ J/KG INTO THE REGION.  EFFECTIVE BULK
SHEAR OF 30 KTS IS HELPING TO ORGANIZE THE CONVECTION INTO A BAND.

HOURLY RAIN TOTALS ARE STARTING TO APPROACH 2" IN THE BAND PER
RADAR IMAGERY.  THE CONCERN IS THAT THIS BAND WILL MOVE OVER
PORTIONS OF THE NC RESEARCH TRIANGLE OVER THE NEXT FEW HOURS WITH
ITS CURRENT INTENSITY BEFORE INSTABILITY FADES.  IT MAY ALSO CROSS
PATHS WITH A PREVIOUS HEAVY RAINFALL FOOTPRINT JUST SOUTH OF ITS
CURRENT TRAJECTORY.  THE MESOSCALE GUIDANCE HAS A TINY SIGNAL FOR
3-4" OF RAIN IN CENTRAL NC; THE LENGTH OF THIS BAND SUGGESTS THAT
THE GUIDANCE MAY BE UNDERPERFORMING.  OVER THE NEXT FEW HOURS,
HEAVY RAINFALL FROM THE BAND COULD THREATEN FLASH FLOOD GUIDANCE
VALUES. 

ROTH

ATTN...WFO...GSP...RAH...

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

LAT...LON   36037834 36027795 35527821 35167872 35027924
            34987949 34928011 35048037 35358038 35577974