225
FXUS62 KCHS 231348
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
948 AM EDT Sat Aug 23 2025

.SYNOPSIS...
A front will remain stalled over the region through Sunday as
waves of low pressure pass by. A much stronger cold front will
clear the area Monday night with high pressure prevailing
through the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Quick update issued to extend the Coastal Flood Advisory to 11
AM.

Complex surface pattern across the region today. The center of a
1020 mb high centered over the Mid-Atlantic states will ridge SW
across the Carolinas and Georgia today. This pattern should support
northeast winds across most of the forecast area today, especially
across the inland counties. High resolution guidance indicates that
the sfc ridge may surge across the CWA this afternoon. In addition,
GOES water vapor shows a vort max over southern GA early this
morning. This mid-level disturbance is expected to track off the
coast of GA by this afternoon, near term guidance indicates that a
coastal sfc low may develop along the wedge front this afternoon.

The environment will continue to feature extremely high moisture
through this evening, PW values around 2.3 inches. A tight gradient
of instability should remain across the forecast area today, with
values as high as 1000-1500 J/kg along the coast. Deep moisture
convergence should remain the greatest along the coast, especially as
the coastal low begins to form this afternoon. The combination of
forcing along the wedge front, instability, and deep moisture should
result in rounds of heavy rainfall today, especially along and east
of I-95. See Hydrology and Climate sections below.

The wedged air mass, thick cloud cover, and rounds of rainfall
should limit heating today. Favoring the cooler MOS, high
temperatures area forecast to range from the upper 70s across the SC
Lowcountry to the low 80s across SE GA.

Tonight, the stable wedge should spread across the CWA as the
coastal low tracks to the northeast. Rainfall should decrease from
west to east through the night. Temperatures may cool to the upper
60s across far inland GA and SC tonight. Most areas will range in
the low 70s.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
Sunday: Somewhat drier air characterized by slightly lower PWATs and
surface dewpoints in the lower 70s vs mid 70s will attempt to advect
in from the northwest Sunday afternoon as a final wave of low
pressure forms along the stalled front and propagates quickly off
the east/northeast. It is unclear exactly how much of this slightly
drier airmass will advect into the Lowcountry and Southeast Georgia
and how much of an impact this will have on convection, but Sunday
will mark the beginning to a change to the overall synoptic pattern.
Even with slightly drier air in place, conditions still look to
support chances for showers/tstms above climatological normals for
late August thanks to lingering surface forcing and weak vorticity
aloft. Models depict the greater rainfall chances to occur along the
coast which are in proximity to the max convergence. The steering
flow does look a bit more progressive suggesting residence times for
the heaviest convective cells will be limited, but wet soil
conditions will extend the risk for isolated flooding. Temperatures
will warm into the mid to upper 80s with min temps in the low to mid
70s overnight.

Monday: A broad, longwave trough will begin to setup over the
eastern CONUS Monday which will linger into much of the upcoming
week. A series of embedded shortwaves will cross the Great Lakes and
Ohio Valley which will help force a cold front across the Southeast
during the day, pushing offshore late Monday night. While the
airmass ahead of the front will slowly dry out with the mean flow
veering more westerly with time, there looks to be enough residual
moisture and instability to support isolated to perhaps scattered
showers/tstms, especially at the coast where low-level convergence
will be somewhat enhanced near a pinned sea breeze circulation. At
this time, the severe threat looks rather low with modest
instability and bulk shear around 20-25 kt, but the environment
could perhaps support an isolated strong storm. Highs will be back
in the upper 80s to lower 90s with some bouts of sunshine returning.
Overnight temperatures will start to become slightly cooler with
mins dipping into the mid to upper 60s inland and lower 70s along
the coast.

Tuesday: Cool, dry high pressure will filter in behind the front
throughout the day. Mostly sunny skies with no mentionable POPs
(less than 15%) are forecast. Temperatures will peak in the mid to
upper 80s with areas near the Altamaha River reaching near 90
degrees.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Broad high pressure will shift over central Appalachian with
the forecast area located within its southeastern fringes. The
greatest moisture should remain offshore and to our south,
resulting in isolated to perhaps scattered showers/thunderstorms
developing mainly along the sea breeze. Otherwise, much drier
conditions are forecast especially for locations inland. Below
normal temperatures are expected through next week.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
12Z TAFs, terminals will remain along the edge of a build sfc
ridge, centered across the western Carolinas. The TAFs will
feature northeast winds with periods of restrictive ceilings.
Rounds of showers and thunderstorms may occur at any time today.
However, the greatest potential for restrictive rainfall rates
will be possible this morning at all the terminals. A coastal
low is forecast to develop this afternoon, tracking to the NE
this evening. In the wake of the low, stable air should increase
from west to east across the forecast area this evening.
Restrictive ceilings may come in and out through the day with
the develop wedge, IFR to MVFR ceilings may become more stable
tonight.

Extended Aviation Forecast: Flight restrictions are likely through
Sunday with numerous showers/tstms. The risk will diminish Monday as
drier air filters into the region behind departing low pressure.

&&

.MARINE...
Today and tonight: The center of a 1020 mb high centered over the
Mid-Atlantic states will ridge SW across the Carolinas and Georgia
today. This pattern should support east-northeast winds across most
of the forecast area today. A coastal low is forecast to develop
over the waters this afternoon, possibly resulting in a surge of NE
wind gusts in excess of 20 kts across the nearshore waters. The low
will depart this evening and overnight, resulting in winds to shift
from the NW. Rounds of heavy rainfall will occur throughout today,
reducing visibility to less than a mile at times.

Sunday through Thursday: Offshore winds will prevail Sunday into
Monday as a weak coastal low departs to the northeast. A cold front
will push offshore late Monday night causing winds to shift out of
the northeast and prevail through the remainder of the period. Both
winds and seas look to remain below Small Craft Advisory levels. No
marine concerns expected through the period.

Rip Currents: A moderate risk for rip currents is in place for
all beaches today due to lingering swells from Hurricane Erin.

&&

.HYDROLOGY...
Showers and thunderstorms produced numerous areas of 3 to 5 inches,
with localized areas receiving in excess of 7 inches, of rainfall on
Friday across southeast Georgia and the South Carolina. An
additional 1.5 to 2.5 inches of rainfall can be expected across the
region through this evening. The heaviest rainfall should occur
generally along and east of the Interstate 95 corridor, some areas
possibly receiving in excess of 4 inches. The additional rainfall
falling on nearly saturated soil will likely lead to rapid runoff,
possibly producing flash flooding.

Several streams and creeks have elevated water levels following the
heavy rainfall that occurred on Friday. Based on the forecast
rainfall, Church Creek near West Ashley, French Quarter Creek near
Huger, and Ireland Creek at Walterboro could see water levels crest
above flood stage. In addition, flash flooding may develop within
coastal cities with any heavy downpours that coincide with high tide
this morning or this evening.

&&

.TIDES/COASTAL FLOODING...
Both the morning and evening tide may produce coastal flooding
today. Departures should remain high enough to result in minor
coastal flooding at the CHS Harbor gauge for the morning high
tide at 8:46 AM. A Coastal Flood Advisory has been issued for
Charleston and coastal Colleton Counties until 10 AM. Steady
ENE winds along with some swell wave run-up may keep departures
in excess of 1 ft this evening. Minor to moderate coastal
flooding is possible at the CHS Harbor this evening. High tide
at 9:04 PM. Fort Pulaski could also peak above flood stage this
evening, depending on the timing and strength of a developing
coastal low.

&&

.CLIMATE...
Record Rainfall:

August 23:
KCHS: 1.98/1995
KCXM: 1.74/1960
KSAV: 4.59/1951

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Flood Watch through late tonight for GAZ087-088-099>101-
     114>119-137>141.
SC...Flood Watch through late tonight for SCZ040-042>045-047>052.
     Coastal Flood Advisory until 11 AM EDT this morning for SCZ049-
     050.
MARINE...None.

&&

$$