884
FXUS62 KCHS 051111
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
711 AM EDT Sat Sep 5 2026

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

&&

.KEY MESSAGES...
- 1) Hot and humid conditions expected this weekend.

- 2) Numerous to widespread thunderstorms are expected to
  develop across the region Sunday afternoon into Sunday night.
  These thunderstorms are expected to bring a risk for damaging
  wind gusts as well as locally heavy rainfall and flooding.

- 3) The potential for coastal flooding will increase starting
  early next week with the threat continuing at least through
  the middle of the week.

&&

.DISCUSSION...
KEY MESSAGE 1: Hot and humid conditions expected this weekend.

Aloft, the eastern extent of high amplitude ridging centered
across the central CONUS will reach into the region today. Then
by Sunday this eastern extent of the ridge will retreat to the
west as troughing spreads into the area. At the surface, the
forecast area will sit ahead of a cold front approaching from
the north today, with the front expected to arrive late Sunday.
For today, temperatures are forecast to peak in the mid 90s.
Dewpoints are forecast to be in the mid to upper 70s along much
of the coastal corridor while mixing out a bit into the low to
mid 70s inland. This combination is expected to yield heat
indices up to around 105 degrees everywhere, with values as high
as 110 degrees across an area that includes nearly all of
southeast SC and potentially even across the Savannah River and
into Effingham and Chatham counties. The ongoing Heat Advisory
looks to be well placed, and some areas within it will be quite
marginal to reach the advisory threshold of 108 degrees.
Therefore, there is no strong support to expand the Heat
Advisory.

Looking ahead to Sunday, another hot and humid day is expected
ahead of an approaching cold front. Temperatures are forecast to
peak in the mid 90s, with some upper 90s possible across
southeast GA. With dewpoints again in the mid to upper 70s along
the coast and low to mid 70s inland, the setup will again
likely yield heat indices into the 105-110 degree range. We
could again see marginal Heat Advisory conditions likely along
the entire coast and even some of inland southeast GA. However,
we expect to see thunderstorm coverage increase quickly in the
afternoon which could complicate the heat index forecast.

KEY MESSAGE 2: Numerous to widespread thunderstorms are
expected to develop across the region Sunday afternoon into
Sunday night. These thunderstorms are expected to bring a risk
for damaging wind gusts as well as locally heavy rainfall and
flooding.

A cold front is forecast to approach the forecast area from the
north Sunday afternoon and then pass through Sunday night.
Ahead of the front, numerous to widespread thunderstorms are
expected to develop in the afternoon and impact the entire
forecast area into the evening. These thunderstorms will bring
the risk of damaging wind gusts as well as intense rainfall.

Severe Weather: Temperatures are forecast to warm into the mid
(and possibly upper) 90s with dewpoints pooling in the mid to
upper 70s along the coast. This will yield moderate to strong
instability within a very moist environment. The front will
provide sufficient convergence to support strong updrafts and
despite the lack of any significant deep layer flow there will
be the potential for clusters of strong storms capable of
producing damaging wind gusts. The severe potential will be
highest where outflow boundary interactions enhance updrafts.
There is little to no confidence in where the best severe
potential will reside spatially, but with the anticipated
coverage the threat will exist across all of southeast GA and
southeast SC. As far as timing, guidance suggests that
convective initiation will take place in the mid afternoon and
the threat will persist until the environment gets worked over
later in the evening.

Heavy Rain: The environment will be quite moist with
precipitable water values in the 2-2.25" range. With strong
convection expected and some enhanced convergence with the
presence of the front, pockets of very intense rainfall are
expected with thunderstorm clusters. Storm motion will not be
particularly fast, likely around 15 knots. The risk for heavy
rain will be highest where clusters track over the same areas
and where boundary interactions produce persistent development.
The 05/00z HREF suggests there will be pockets of 30-50%
probabilities of 3+ inches in a 3 hour period, which will bring
the risk of flash flooding to the area. The risk will be highest
in urbanized areas and will extend through the evening. The
potential for locally heavy rain will decrease into Monday as
less coverage is expected and less instability will be
available.

KEY MESSAGE 3: The potential for coastal flooding will increase
starting early next week with the threat continuing at least
through the middle of the week.

Astronomical tides will continue to rise through the middle of
next week thanks to the lunar perigee (9/6) and the upcoming new
moon (9/11). These factors will push astronomical tides as high
as 6.55 ft MLLW at Charleston with the Wednesday evening high
tide, setting the stage for the coastal flooding potential with
meteorological support. A cold front will push through Sunday
night and an extended period of elevated northeast flow is
expected from Monday into Wednesday which will drive increased
tidal departures. Coastal flooding will be favored during the
evening high tide cycles at Charleston and could begin as early
as the Monday evening high tide. While minor coastal flooding is
the most likely scenario, the potential for moderate coastal
flooding will increase with the Tuesday and Wednesday evening
high tides. Coastal Flood Advisories will likely be needed for
Charleston and coastal Colleton counties.

For the rest of the coast for Beaufort County and the southeast
GA coast, tidal departures would need to exceed 1 ft to reach
the minor coastal flood threshold (9.5 ft MLLW) at Fort Pulaski.
So, coastal flooding is less likely in this area but still
can`t be ruled out especially if the northeast flow behind the
passing cold front turns out a bit stronger than currently
forecast.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
The 12z TAF period begins with VFR conditions at KCHS, KJZI,
and KSAV. So far this morning, fog and stratus has remained
inland of KSAV. There is still time for stratus to spread in
just after sunrise, but it certainly looks less likely that
there will be any flight restriction impacts. Thunderstorm
potential for the afternoon and evening is quite low and there
is no support to include anything in the TAF`s at this time.
Late this evening there are some hints in model guidance that an
outflow boundary from thunderstorm activity to the north will
push down into the area and could kick off some showers or even
a thunderstorm. Confidence in this actually occurring is low so
we have no added it to the forecast as of yet. If a few showers
or thunderstorm were to develop, it would likely be near KCHS or
KJZI.

Extended Aviation Outlook: The potential for impacts from
thunderstorms will increase late Saturday night and likely peak
Sunday evening and Sunday night as a front drops into the area.
Periodic flight restrictions will remain possible into early
next week due to showers and thunderstorms. Also, breezy
conditions could develop with increasing northeast flow early
next week.

&&

.MARINE...
Today through tonight: Light westerly flow this morning will
turn more southerly with the onset of the sea breeze this
afternoon and evening along the land/sea interface. Then through
the overnight, southwest flow will prevail across the local
waters. Wind speeds should mostly be in the 10-15 knot range,
but could gust up to around 20 knots at times in the evening and
the first part of the overnight with some modest nocturnal
surging. Seas are expected to be in the 2-3 ft range through the
period.

Sunday through Wednesday: A cold front is expected to drop
southward through the waters Sunday night. Behind the front, a
solid surge of northeast flow is expected. Winds will peak
Monday through Tuesday with sustained wind speeds around 20
knots and gusts around 25 knots. Seas will steadily build in the
persistent northeast flow as well, with 5+ ft expected
everywhere and even 6-7 ft spreading across much of the waters.
This combination of winds and seas will almost certainly bring
the need for Small Craft Advisories beginning Monday morning and
continuing through Tuesday and possibly even Tuesday night.
Charleston Harbor will likely be included in these advisories as
well, especially with some diurnal surging in the afternoon and
evening Monday and Tuesday.

Along the front, there will be the potential for strong
thunderstorms across the local waters Sunday and Sunday night.
These storms will bring the potential for strong wind gusts in
excess of 35 knots as well as frequent lightning.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for GAZ101-218-219.
SC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for SCZ042>045-147>152.
MARINE...None.

&&

$$