240
FXUS62 KCHS 040623
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
223 AM EDT Mon Aug 4 2025

.SYNOPSIS...
A stationary front will linger near the area this week as high
pressure remains centered well to the north. Low pressure could
develop off the Southeast U.S. coast Thursday into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Prior to daybreak: Scattered/numerous showers will continue across
parts of Southeast Georgia into far Southern South Carolina, with
some hires guidance suggestion an uptick in coverage late night as
weak isentropic lift occurs in a very moist (PWATs around 2.25
inches) environment. Instability remains rather weak across land
during this time frame, suggesting thunderstorm activity and/or
heavy rainfall to be more limited than the previous night. However,
stronger northeasterly winds across coastal waters should favor
enhanced moisture convergence along coastal areas and perhaps drive
modest instability onshore, supporting brief downpours from
showers/thunderstorms. Although Flash Flooding is not anticipated at
this time, conditions could eventually support Flood Advisories
across coastal communities near Savannah, GA to Beaufort, SC prior
to daybreak. Low temps remain on track to dip into the upper 60s
inland to mid 70s closer to the coast.

Today: Aloft, a weak mid-lvl trough will progress east across the
Midwest, favoring h5 shortwave energy to ripple across the Southeast
United States. At the sfc, high pressure will persist across much of
the local area while a front remains nearly stationary across
northern Florida. The setup will favor conditions quite similar to
those experienced the previous day, with ample moisture (PWATS near
2.25 inches) residing across much of the area, enhanced moisture
convergence near the coast, and weak isentropic lift/h5 shortwave
energy providing forcing to support scattered to numerous
showers/thunderstorms. Precip coverage should be largest during peak
diurnal heating hours this afternoon and perhaps persist into early
evening. Activity should initially be more focused across coastal
areas this morning, before developing across inland areas as h5
shortwave energy and weak isentropic lift shift/occur across sfc
high pressure. Although instability is rather meager (especially
inland) with high pressure supporting slightly cooler conditions
within a northeast sfc flow and storm motions appear slightly faster
than previous days, the abundance of moisture and forcing could
support bouts of heavy downpours with showers/thunderstorms, and
eventually require Flood Advisories and/or Flash Flood Warnings for
activity that resides over an area for a longer duration. WPC
currently has much of Southeast Georgia in a Slight Risk for
excessive rainfall, and Marginal Risk extending north across coastal
areas into Southeast South Carolina.

Abundant cloud cover and persistent shower and/or thunderstorms
coverage will help keep afternoon highs a bit cooler this afternoon,
especially within the high pressure/northeast sfc flow pattern. In
general, high temps should range in the upper 70s well inland to low-
mid 80s across Southeast Georgia and along/east of I-95 across
Southeast South Carolina.

Tonight: Much like the previous few night, shower and thunderstorm
activity could linger into evening hours, but should gradually wane
with the loss of diurnal heating while the sfc high pressure pattern
remains in place. At the very least, the threat for heavy rainfall
potential should become more limited inland as instability is weak
within high pressure. However, given the abundance of moisture, few
to scattered showers remain possible into early morning hours.
Closer the coast, moisture convergence and modest instability across
the nearby Atlantic could support additional bouts of downpours with
showers/thunderstorms and the potential need for Flood Advisories
and/or Flash Flood Warnings overnight. Low temps should range in the
upper 60s inland to low-mid 70s closer to the coast.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
The anomalously strong high pressure wedge will hold for much of the
week as the region remains pinned between subtropical ridging
offshore of the Southeast U.S. and a filling longwave trough
extending from the Ohio Valley south into the lower Mississippi
Valley. Ribbons of vorticity ejecting north across the Southeast
U.S. ahead of the weakening longwave coupled with typical diurnal
instability and the nearby quasi-stationary wedge front just to
south/offshore will support numerous showers/tstms each day with the
greatest coverage occurring across Southeast Georgia.

Model cross sections suggest forcing/UVVs from these impulses will
not be overly deep or strong, but with a plume of high PWATs in
place (2.00-2.25") holding in place and fairly low convective
temperatures each day, it will not take too much for convective
initiation to occur. Convection each day will likely be largely
driven by numerous mesoscale boundary interactions, including
convective outflow boundaries and the afternoon sea breeze.
Convection will be slow to wane during the evening hours each day
with a risk for at least isolated showers/tstms lingering through
the night. The forecast becomes a bit more uncertain beginning
Thursday with low pressure possibly developing off the Southeast
U.S. coast. Afternoon highs (mid 80s to around 90) will remain
slightly below normal for early August given the considerable amount
of convection and debris cloud cover that will occur each day.
Overnight lows (upper 60s well inland to lower 70s at the coast)
will average at or just slightly below normal.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Guidance is starting to show a slightly stronger signal that an area
of low pressure will develop off the Southeast U.S. coast by late in
the week into the weekend as a Tropical Upper Tropospheric Trough
(TUTT) propagating westward along the southern flanks of the
subtropical upper-level anticyclone over the central north Atlantic
approaches the Bahamas. Much of the forecast will hing on this
feature with its character, strength, timing and track still highly
uncertain. The National Hurricane Center currently shows a low
chance for tropical cyclone development. For now, the forecast
remain aligned with the 04/01z NBM, which keeps unsettled conditions
in place in the Friday to Sunday time period.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
CHS/JZI: VFR conditions should prevail through 12Z Monday, before
TEMPO MVFR cigs and light showers are possible in the 12-15Z Monday
timeframe. Confidence is low in regards to timing of additional
showers and/or possibly thunderstorms during the afternoon time
frame, but VCSH has been placed at the CHS terminal between 19-23Z
and JZI terminal between 19-01Z today/tonight. JZI appears to have
the higher potential of flight restrictions late in the TAF period
and future adjustments will likely be needed for convective trends.

SAV: TEMPO IFR conditions are possible with ongoing showers across
the terminal until around 07Z. Outside of this convection, periods
of MVFR cigs are likely through 06Z Tuesday with additional showers
and/or thunderstorms temporarily producing low-end MVFR and/or IFR
conditions at the terminal. Confidence is too low in regards to
timing to include additional shower and thunderstorm activity, but
future TAF adjustments will likely be needed for convective trends.

Extended Aviation Outlook: An elevated risk for flight restrictions
from showers/tstms will persist for much of the week.

&&

.MARINE...
Prior to daybreak: A modestly enhanced pressure gradient
between high pressure nudging into the area north and a front
positioned across northern Florida will support gusty northeast
winds (15-20 kt) across nearshore waters prior to daybreak and
the potential for a few wind gusts up to 25 kt across nearshore
waters during the next few hours. Given winds should gradually
trend weaker, conditions do not support a Small Craft Advisory
at this time. Seas will range between 3-5 ft, largest across
Charleston County waters beyond 15 nm and across outer Georgia
waters.

Today and Tonight: Overall, the setup remains similar to that
experienced the previous day with high pressure placed inland and a
nearly stationary front south of the local area. A slightly enhanced
pressure gradient across local waters supports northeasterly winds
around 15 kt with gusts around 20 kt through the day, but the
gradient is expected to weaken during the afternoon into the
evening, suggesting winds to lower to 10-15 kt and turn more east
overnight. Seas will slowly subside to 2-4 ft as winds weaken
through the night.

Tuesday and Wednesday: There are no immediate high confidence
concerns. East to northeast winds will prevail for much of the
period as an inland wedge of high pressure prevails. Occasional
pinching of the pressure gradient is likely, but winds will
generally remain 15 kt or less outside of convection through
Wednesday. Seas will average 2-4 ft.

Thursday through Saturday: Much will depend on how strong low
pressure that could form off the Southeast U.S. coast gets. East to
northeast winds will continue, but speeds as well as waves/swell may
become enhanced depending on the eventual track, strength and speed
the low takes.

Rip Currents: Some elevated swell and continued northeast flow will
yield a Moderate Risk of rip currents for the GA beaches on today.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

$$

NEAR TERM...DPB
SHORT TERM...
LONG TERM...
AVIATION...DPB
MARINE...DPB