MESOSCALE PRECIPITATION DISCUSSION 0809
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
850 AM EDT TUE SEP 12 2017

AREAS AFFECTED...SERN NC

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

VALID 121248Z - 121615Z

SUMMARY...LINGERING TRAINING BANDS OF HEAVY RAIN WILL CONTINUE A
THREAT FOR FLASH FLOODING FOR PORTIONS OF SERN NC THROUGH 16Z.
LOCALIZED ADDITIONAL RAINFALL TOTALS OF 3-5 INCHES ARE EXPECTED..

DISCUSSION...STRONG LOW LEVEL MOISTURE TRANSPORT CONTINUES TO
FOCUS MODERATE TO LOCALLY HEAVY RAINFALL INTO ERN NC. KLTX RADAR
AS OF 12Z CONTINUED TO SHOW THE HEAVIEST RAINFALL RATES...1-3
COUNTIES INLAND FROM THE COAST FOR LOCATIONS JUST WEST OF I-40.
DUAL-POL ESTIMATES WERE NEAR OBSERVATIONS OF 1.5 TO 2.5 IN/HR.
THESE HEAVIER RAINFALL RATES WERE LOCATED AT THE LEADING EDGE OF A
DEWPOINT GRADIENT LOCATED SEWD FROM NERN SC AND WERE LIMITED BY A
LACK OF INSTABILITY FARTHER INLAND ON THE COOL SIDE OF A
STATIONARY FRONT SEPARATING HIGHER THETA-E AIR FROM COASTAL
LOCATIONS FROM THOSE FARTHER INLAND.

AS THE SURFACE LOW TIED TO POST-TROPICAL CYCLONE IRMA CONTINUES TO
SLOWLY MOVE NORTHWEST FROM NRN AL OVER THE NEXT 3-6 HOURS...LITTLE
CHANGE TO THE COASTAL FRONTAL BOUNDARY AND INSTABILITY AXIS IS
EXPECTED. ONSHORE WINDS WHICH ARE CURRENTLY 20-30 KT PER VAD WIND
DATA FROM KLTX AND KMHX ARE FORECAST TO WEAKEN A LITTLE AS DRIER
AIR NOTED ON WATER VAPOR IMAGERY CONTINUES TO PUSH NORTH THIS
MORNING ACROSS THE REGION WHICH ALONG WITH DECREASING LOW LEVEL
CONVERGENCE SHOULD ALLOW THE HEAVY RAINFALL THREAT TO CONTINUE TO
DIMINISH THROUGH 16Z. UNTIL THEN HOWEVER...ANOTHER FEW HOURS OF
LOCALLY HEAVY RAIN IS EXPECTED FOR PORTIONS OF SERN NC WITHIN
NARROW AXES OF TRAINING HEAVY RAIN WHICH MAY CAUSE LOCALIZED FLASH
FLOODING.

OTTO

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

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

LAT...LON   35597716 35327685 34937677 34527686 34167726
            33797784 33867828 34047854 34767868 35287822
            35577780