453
AWUS01 KWNH 161443
FFGMPD
NCZ000-SCZ000-162045-

Mesoscale Precipitation Discussion 1022
NWS Weather Prediction Center College Park MD
1042 AM EDT Mon Sep 16 2024

Areas affected...Southeastern NC...Eastern SC...

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

Valid 161445Z - 162045Z

SUMMARY...Potential T.C. Eight.  Add`l 4-8" possible, likely
resulting in expanding flash flooding area; localized considerable
flash flooding is likely as well.

DISCUSSION...Sizable rainfall totals over 6"+ have been reported
since midnight across portions of far southeastern North Carolina
this morning resulting in flash flooding conditions.  14z surface
obs and remote sensing suite depict the surface center of PTC
Eight is about 60-70 nmi southeast of Myrtle Beach, showing fairly
solid frontal structure with a well defined cold front associated
low-topped tropical shower line along the northeast and eastern
quadrants before angling along the Gulf Stream back to Florida.
Theta-E gradient also depict a sharpening warm front parallel to
the SC/NC coast to around Cape Fear before extending more
eastward, but has been showing a trend of north-northwestward
translation over the last few hours.  This is expanding the warm
sector which is well defined with a axis of enhanced MLCAPE
increasing to 1500-2000 J/kg with a fairly saturated narrow skinny
profile, though there is a bit of mid-level dry air nosing in
along the southwest side.  Along/north of the boundary the
effective cool conveyor belt is fully saturated through depth with
total PWat values over 2" reaching 2.25"; so with a highly
convergent low level profile an strong instability; deep
convection is likely to further develop/maintain through the late
morning into the afternoon hours with the capability of 2-3"/hr
rates (perhaps locally higher in short-duration) as convergence
waves move through the warm sector/TROWAL.  Given proximity of the
warm front to the coastline, slow northward expansion of these
stronger highly efficient showers, but may be more inconsistent in
timing with reduced low level moisture convergence relative to
Brunswick/New Hanover counties. An additional 4-8" are possible
through the next 6 hours and considerable flash flooding will
likely become more common across these counties.

Further ashore...a mesoscale low/wave could be seen within the
coastal observations along the southern coast of Brunswick county
as well as within KLTX RADAR and appears to be strongly convergent
along the western edge of the low to mid-level TROWAL. Given
orientation to the core vorticity center that has recently rotated
under the eastern edge of the canopy (noted by reduced warm temps
in the WV suite); the wave will likely slow and translate a bit
south of due west.  The remaining strong moisture flux convergence
but stabilizing air, will maintain enhanced rain rates but will
reduce into the 1-2"/hr range but likely have some training given
the orientation of the TROWAL should be consistent to expand heavy
rainfall footprint toward Dillon counties in SC and
Robeson/Columbus counties in NC with very slow northward
translation expected.  Totals of 2-4" over the next 6hrs are
possible and should expand flash flooding problems that way as
well with time.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

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

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

LAT...LON   35147832 35057741 34967685 34787644 34577652
            34617684 34547718 34427746 34217769 33977780
            33817802 33827837 33787887 33977988 34388018
            34818004 35027932