Mesoscale Precipitation Discussion 0847
NWS Weather Prediction Center College Park MD
1214 AM EDT Sun Sep 16 2018

Areas affected...south-central NC into southeastern NC and eastern
SC

Concerning...Heavy rainfall...Flash flooding likely

Valid 160413Z - 160955Z

Summary...Localized 3-6 inch maxima (6 hour totals) are expected
across far southeastern NC through 10Z. Rainfall of this magnitude
will only exacerbate the already catastrophic/life-threatening
flooding conditions ongoing across the Carolinas.

Discussion...The 03Z NHC advisory placed T.S. Florence over
east-central SC, roughly 40 miles ESE of Columbia. A persistent
narrow rain band or two has continued to affect southeastern NC
over the past several hours with rainfall rates peaking between
2-3 in/hr at times. The SPC mesoanalysis page showed little change
in MLCAPE over the past 3 hours ending 03Z for both inland and
offshore locations. 500-1000 J/kg was estimated to be in place
over Horry, Columbus, Brunswick, New Hanover and Pender counties,
with these locations supporting the heaviest rain rates as of
0330Z. VAD wind plots and RAP analyses supported 40-50 kt of 850
mb flow perpendicular to the SC/NC coast, with a 2.8 inch
precipitable water observation sampled by a GPS sensor between
Charleston and Myrtle Beach at 02Z. Farther inland across interior
northern SC, instability has been weaker but steady rain rates of
0.5 to 1.0 in/hr have allowed 3-6 inches of rain over the past 24
hours while storm totals into southeastern NC have eclipsed 20
inches in some areas.

A continued slow west to northwestward movement of Florence is
expected through the morning with a gradual westward expansion of
the existing CAPE axis along the NC/SC coastal border. This should
allow the translation of or re-development of the rain band with
1-3 in/hr rates and repeating cores to the west of its present
location, possibly impacting Horry, western Columbus and western
Brunswick counties by 10Z. Within about 70 miles of the coast, an
additional 3-6 inches of rain are expected while for locations
farther inland, a longer duration rain with rates up to 1 in/hr
will support a continued flood/flash flood threat and 2-4
additional inches of rain through 10Z.

Otto

ATTN...WFO...CAE...GSP...ILM...MHX...RAH...

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

LAT...LON   35697976 35577887 35367811 34987754 34277694
            33717745 33127828 33107905 33717936 34177994
            34648112 35018133 35448130 35658068