Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Dec 17 2023 16:08:21

AWUS01 KWNH 171608
FFGMPD
NCZ000-SCZ000-172200-

Mesoscale Precipitation Discussion 1203
NWS Weather Prediction Center College Park MD
1107 AM EST Sun Dec 17 2023

Areas affected...Eastern SC...Southern NC

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

Valid 171600Z - 172200Z

Summary...1-2"/hr rainfall rates to increase in coverage,
resulting in localized totals of 4-8" over the next 6 hours.
Isolated to scattered instances of flash flooding are likely, and
some instances of flash flooding may be significant (especially
combined with coastal flooding along the SC coastline).

Discussion...Steady moderate to heavy rainfall continues in
association with a deepening low pressure system over the
Southeastern CONUS, as impacts in the near term are focusing
across the Carolinas (in the northeastern quadrant of the
cyclone). Very strong low-level moisture transport is resulting in
rapidly increasing instability (per 300-400 J/kg increase of ML
CAPE just offshore of SC over the past 3-hr), and embedded
convective elements along and ahead of the warm front are expected
to result in an increase in coverage of 1-2"/hr rates (over areas
that have already realized 1-4" of rainfall over the past 3-6
hours). PWATs have already increased to near 1.7" along the coast
(near the max moving average, per CHS sounding climatology), and
repeating 1-2"/hr rates could lead to localized totals over the
next 6-hr of 4-8" across much of coastal SC (including Charleston
and Myrtle Beach).

While these expected localized totals over 3-6 hours are likely to
lead to flash flood exceedance (which generally corresponds to
2-3" across the region), impacts may well be locally significant
given the addition of coastal flooding along the immediate
coastline. This has already been emphasized by the Charleston WFO,
noting in a Flash Flood Warning that a major high tide is in
progress in the Charleston Harbor. Due to this combined flooding
threat, communities along the coast should be especially aware of
rapidly changing weather conditions and new warnings coming from
the local forecast offices. Isolated to scattered instances of
flash flooding are considered likely in association with the swath
of training heavy rainfall rates, which has the highest likelihood
of occurring across eastern coastal SC (and may extend into
adjacent portions of coastal NC).

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!_eopAAYQmvi6dcMg3cXPZyU1o2965jF_kxvXcIVYR6tCZmgfrKjo6tm_jmaIWHk9bCHd=
A6YZofL8DtNbD3Z8fqBFQUE$  for graphic product...

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

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

LAT...LON   35167896 35057778 34847729 33857757 32887873=20
            32137997 31988080 33368169 34988000=20

=3D =3D =3D
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