Mesoscale Precipitation Discussion 0849
NWS Weather Prediction Center College Park MD
1045 AM EDT Sun Sep 16 2018

Areas affected...Northern SC... Southern NC...

Concerning...Heavy rainfall...Flash flooding possible

Valid 161445Z - 162045Z

SUMMARY...Expected increase/backbuilding of inner core band of TD
Florence which will train over recently highly flooded areas
further compounding life-threatening flooding conditions.

DISCUSSION...GOES-East 1-minute imagery and regional RADAR
reflectivity mosaic depict the center of Florence near the
Saluda/Edgefield/Aiken county intersection lifting NNW.  WV suite
denotes an elongation of the mid-level circulation with a
vorticity lobe rotating along the eastern quadrant of Florence. 
The inner band, enhanced in the lower levels by the cyclonic
branch of the warm conveyor, is showing increased convective
activity starting to backbuild toward the SSE.  Strong sfc
moisture convergence with coastal winds of 15-25kts and Tds in the
upper 70s/lower 80s fed by the Gulf Stream Current supports
MLCAPEs in this band as high as 2500 J/kg tapering off to around
100-250 J/kg near KCLT.  Strong enhanced low level inflow will
support upstream redevelopment of this band and given 2.4" total
PWATs and mean mixing ratios over 18 kg/kg.  This should support
rain rates in excess of 3"/hr near the coast.  Mean cell motions
will support training especially towards a confluence point near
CLT as well, otherwise, the band along with the upper level
forcing should support slow but northward propagation with time,
perhaps reaching the NC/SC border toward 20z-21z. This should
support sections of the band to have an additional 4-6"
(Dillon/Marlboro to Horry counties) and 2-4" likely further
upstream into south central NC.  Isolated totals greater than 8"
are possible especially with greatest vertical development and
longest training likely near coastal counties.  This is in line
with the ARW and recent HRRR evolution providing solid confidence
to these extreme totals unfolding. 

Farther north...stronger frontogenetic forcing is increasing from
Rowan to Onslow county in the 850mb zone...strengthening northerly
component and aforementioned DPVA from vort center rotating north
should strengthen low level flow/confluence for this FGEN forcing.
 While instability is a bit reduced and moisture convergence is
less than further south, efficient modest 1"/hr rainfall with
isolated higher amounts from lingering convective elements within
the band should further compound already flooded regions, though
with an additional 2-3" totals likely with potentially 4" totals
nearer the coast of New Hanover to Onslow county. 

Gallina

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

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

LAT...LON   35908033 35557853 35117750 34587701 33857787
            33747855 33227904 33037929 33688007 34328051
            35108154 35728124