412
AWUS01 KWNH 240121
FFGMPD
SCZ000-GAZ000-240720-

Mesoscale Precipitation Discussion 0989
NWS Weather Prediction Center College Park MD
920 PM EDT Sat Aug 23 2025

Areas affected...Coastal SC/GA

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

Valid 240120Z - 240720Z

SUMMARY...New bands of heavy showers and a few thunderstorms may
focus along coastal areas of SC and GA overnight bringing a new
threat of flash flooding.

DISCUSSION...The early to mid-evening satellite imagery along with
surface data shows an area of low pressure beginning to take shape
along a frontal zone just off the SC/GA coast. This area of low
pressure is forecast tonight to gradually lift off to the
northeast, but be not far offshore of the SC Lowcountry. The
latest suite of guidance including the evening runs of the
experimental WoFS suggest the low center becoming better defined
and strengthening a tad along the front which should facilitate an
increase in low-level moisture convergence back into the coastal
areas of SC and GA.

An instability gradient along with an inverted surface trough is
already noted along the coast, and radar imagery is showing a new
band of warm-topped convection advancing westward back into some
of the coastal areas of the SC Lowcountry, with some separate
slow-moving cells over far eastern GA.

The recent runs of the WoFS have been trending toward somewhat
greater concentrations of warm-topped convection along the coast
over the next several hours with a trend toward somewhat heavier
rainfall totals. Some of the recent HRRR guidance has also
exhibited a similar trend.

Given the highly tropical environment with PWs of 2.2 to 2.4
inches, the rainfall will be very efficient with some of these
warm-topped convective bands capable of rates reaching 2+
inches/hour. A localized concern for cell-training will exist as
well, and thus some additional rainfall totals of as much as 3 to
5 inches cannot be ruled out overnight right along the immediate
coast.

Additional areas of flash flooding for the coastal communities
will be possible as a result, and especially with the already
saturated soil conditions and concerns locally with tidal
flooding/inundation.

Orrison

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

ATTN...WFO...CHS...ILM...JAX...

ATTN...RFC...ALR...NWC...

LAT...LON   33677907 33457879 32867953 32278038 31478102
            30948124 30958159 31508155 32318107 33118012