MESOSCALE PRECIPITATION DISCUSSION 0655
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
246 PM EDT TUE AUG 08 2017

AREAS AFFECTED...EASTERN SC...SOUTHEAST NC

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

VALID 081845Z - 090000Z

SUMMARY...LOCALLY VERY HEAVY RAINFALL IS EXPECTED THIS AFTERNOON
ALONG THE IMMEDIATE NC/SC COASTAL PLAIN. SOME RUNOFF AND/OR FLASH
FLOODING IS POSSIBLE.

DISCUSSION...RAPIDLY COOLING CONVECTIVE TOPS ARE NOTED IN
NON-OPERATIONAL GOES-16 IR DATA THIS AFTERNOON OVER EASTERN SC AND
SOUTHEAST NC IN ASSOCIATION WITH AN APPROACHING COLD FRONT THAT IS
INTERACTING WITH A VERY MOIST AND UNSTABLE AIRMASS POOLED RIGHT
ALONG THE IMMEDIATE COASTAL PLAIN. AS PER THE LATEST RAP
ANALYSIS...DIURNAL HEATING HAS HELPED TO CONTRIBUTE MLCAPE VALUES
OF 1500 TO 2500 J/KG RIGHT ALONG THE COAST. THE CONVECTION IS ALSO
BEING AIDED BY SOME RIGHT-ENTRANCE REGION JET DYNAMICS WHICH IS
FOSTERING LARGER SCALE ASCENT IN CONJUNCTION WITH THE FAVORABLE
THERMODYNAMICS.

THE COLUMN IS QUITE MOIST WITH PWATS RUNNING AS HIGH AS 2.25
INCHES...AND GIVEN THE ENHANCED CONCENTRATION OF MOISTURE IN THE
700/300 MB LAYER...RAINFALL PROCESSES WILL BE HIGHLY EFFICIENT FOR
ENHANCED RAINFALL RATES THAT COULD APPROACH 3 INCHES/HR.

THE CONVECTION THAT IS ONGOING AT THIS TIME IS EMBEDDED WITHIN A
RELATIVELY UNIDIRECTIONAL FLOW REGIME AHEAD OF THE COLD FRONT THAT
IS CONDUCIVE FOR SOME TRAINING CONVECTIVE BANDS. THE 12Z ARW/NMMB
SOLUTIONS APPEAR TO BE LOCALLY UNDERDONE GIVEN THE VERY
MOIST/UNSTABLE ENVIRONMENT AND POTENTIAL FOR TRAINING...BUT THE
12Z NSSL-WRF AND RECENT HRRR RUNS APPEAR TO HAVE A SOMEWHAT BETTER
HANDLE OF THE CURRENT ACTIVITY.

EXPECT LOCALLY VERY HEAVY RAIN OVER THE NEXT SEVERAL HOURS AS
MULTIPLE BANDS OF CONVECTION SET UP ALONG AND JUST INLAND OF THE
COAST GOING INTO THE EARLY EVENING HOURS. GRADUALLY ALL OF THE
CONVECTION SHOULD BEGIN TO SHIFT OFFSHORE...BUT NOT BEFORE SOME
AREAS SEE AS MUCH 3 TO 6 INCHES OF RAIN. SOME RUNOFF AND/OR FLASH
FLOODING PROBLEMS WILL BE POSSIBLE.

ORRISON

ATTN...WFO...CAE...CHS...ILM...MHX...RAH...

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

LAT...LON   35187691 34667669 34427712 34147766 33857790
            33697866 33347906 32637991 32188076 32368130
            32878139 33338101 33698050 34287950 34877825