820
FXUS62 KCHS 302307
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
707 PM EDT Wed Sep 30 2026

.WHAT HAS CHANGED...
All sections have been updated.

&&

.KEY MESSAGES...
- 1) Dense fog possible tonight across interior Southeast South
  Carolina and Southeast Georgia.

- 2) The coastal flood risk will linger through the end of this
  week. Another round of coastal flooding is possible next
  week.

- 3) Unsettled weather will return Friday through Monday. Cooler
  temperatures along with breezy to windy conditions are likely
  next week.

&&

.DISCUSSION...
KEY MESSAGE 1: Dense fog possible tonight across interior
Southeast South Carolina and Southeast Georgia.

Broad high pressure over the region tonight will bring clear skies
and calm winds, creating ideal conditions for fog development. As
temperatures drop late tonight, fog is expected to form across most
locations away from the immediate coast. Guidance indicates fog
could become dense (visibilities below 1/4 mile) with the
highest chance across the inland Tri-County area (Charleston,
Berkeley, and Dorchester counties) and portions of far interior
southeast Georgia. A Dense Fog Advisory could be needed if these
trends continue overnight. Fog should dissipate within 1 to 2
hours after sunrise Thursday morning.

KEY MESSAGE 2: The coastal flood risk will linger through the
end of this week. Another round of coastal flooding is possible
next week.

Astronomical tides continue to run higher than normal due to the
recent full moon. Combined with the build up of tidal waters across
inland waterways, and a possible slowing of the Gulf Stream,
coastal flooding will pose a risk through the end of the week,
especially at the Charleston Harbor. Minor coastal flooding is
forecast with the late morning/early afternoon high tides both
Thursday and Friday. Coastal flooding is not a concern at Fort
Pulaski.

Breezy to windy northeast winds induced by strong cold air damming
combined with already high astronomical high tides will likely
result in some saltwater inundation issues next week. There is even
a possibility that gale force winds offshore could help push water
levels well into minor flood levels, possibly even moderate or
higher. Coastal Flood Watches, Warnings and Advisories could be
needed.


KEY MESSAGE 3: Unsettled weather will return Friday through Monday.
Cooler temperatures along with breezy to windy conditions are likely
next week.

The forecast philosophy for this weekend into much of next week has
changed little since Tuesday afternoon. Moisture values will
steadily increase during the period, beginning Friday then peaking
Sunday into Monday as a cold front drops south into the region. PWAT
values are expected to max out in the 2.25-2.40" during this time
which is near to just above 2 standard deviations above normal for
early October and near/at record levels at KCHS per the SPC sounding
climatology for observations taken at 00z. Guidance still shows a
weak, mostly sheared southern stream shortwave traversing the
Southeast U.S. Monday with the front moving through. Deep-layered
forcing for ascent with this feature still looks weak given the lack
of strong DCVA aloft, but some modest low-level UVVs are noted along
the front itself, likely because the frontal zone is exhibiting an
anafrontal signal. The period of greatest rainfall looks to
concentrate Sunday afternoon into Monday afternoon as the front
pushes through, but there is still some timing uncertainty with
fairly large 6-hr QPF interquartile ranges (IQR), as much >0.50-
0.75", still being seen across the entire GFS and ECMWF ensemble
suite. While the risk for measurable rainfall is increasing,
specific amounts are highly uncertain.

Strong cold air damming (CAD) is looking increasingly certain from
Tuesday on with some signals for possible cyclogenesis occurring
offshore as strong high pressure wedges south across the Carolinas
and Georgia. There are unknowns with respect to the strength and
location of any offshore low and how it could impact the pressure
gradient over the area. Even if the low itself does not develop,
guidance has been pretty consistent with showing a fairly tight
gradient developing within the CAD region with possible gales over
the coastal waters. This would likely yield breezy to possibly windy
conditions across much of the Lowcountry and Southeast Georgia with
the highest winds occurring along the coast. Cool conditions will
occur for much of next week with temperatures returning to below
normal levels. Highs both Tuesday and Wednesday could struggle to
get out of the 60s with overnight lows dropping into the 40s in
places, especially across the interior.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
0Z TAFs: Terminals should remain VFR this evening, with winds
become light a variable by mid-evening. Mostly clear and light
to calm winds are forecast across the region tonight.
Radiationalcooling should allow late night temperatures to
reach or exceed cross-over temperatures, especially at KSAV.
Recent runs of the HRRR indicates that the lowest values of sfc
condensation pressure deficits will remain across inland SC and
portions of inland GA. The TAFs will generally feature ground
fog at KCHS, KJZI, and KSAV starting at 7Z, with the lowest
visibility between 10-12Z highlighted with TEMPOs. Thin fog
should dissipate during the first hour or two of daylight
Thursday morning. A weak sea breeze is expected to shift winds
from the southeast beginning in the early afternoon hours.

Extended Aviation Outlook: Flight restrictions in showers and
thunderstorms are possible over the weekend into early next week.

&&

.MARINE...
Today Through Friday Night: Quiet marine conditions will
prevail across the local waters through the remainder of the
week with winds 10 kt or less and seas 1-2 ft.

Saturday through Monday: East to southeast wind regime will dominate
through the weekend with subtropical high pressure centered well
offshore. Local sea breeze enhancements are possible each afternoon
over Charleston Harbor and along the land/sea interface. Winds will
generally remain 10 kt or less, except locally higher within the sea
breeze, with seas 1-3 ft.

Monday Night: A cold front will drop through the waters Monday with
increasing northeast winds likely Monday night as the post frontal
gradient begins to tighten. Small Craft Advisory conditions are
likely (winds at least 25 kt) with gale force winds possible
(especially over the offshore waters), but the risk for gales looks
strongest on Tuesday, which is just outside of this forecast
cycle.

&&

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

&&

$$