252
FXUS62 KCHS 061854
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
254 PM EDT Sun Sep 6 2026

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

&&

.KEY MESSAGES...
- 1) Numerous to widespread thunderstorms are expected to impact
  southeast Georgia and southeast South Carolina this afternoon
  and evening. These thunderstorms will bring a risk for
  damaging wind gusts as well as locally heavy rainfall and
  flooding.

- 2) The potential for coastal flooding will increase beginning
  Monday and persist through the middle of the week.

&&

.DISCUSSION...
KEY MESSAGE 1: Numerous to widespread thunderstorms are
expected to impact southeast Georgia and southeast South
Carolina this afternoon and evening. These thunderstorms will
bring a risk for damaging wind gusts as well as locally heavy
rainfall and flooding.

The forecast continues to focus on the potential for widespread
thunderstorms to produce severe weather and heavy rainfall this
afternoon and evening. There have been some changes to the
original forecast and where the focus for storms are. The
overall pattern has drier northwesterly starting to move into
the area as a broad upper trough digs into the Mid-Atlantic. A
subtle shortwave currently over the Ohio Valley will eject this
afternoon and evening over North Carolina and round the base of
the upper trough. A rather stable airmass is in place across the
area as outflow from yesterdays storms has laid down a boundary
that extends from around Beaufort SC westward towards Atlanta.
This boundary will likely play a role in where the best chance
for both severe weather and heavy rainfall will setup. Storms
have already begun to develop along the warm side of this
boundary across eastern GA and are expected to spread
throughout the afternoon and into the early evening across
eastern GA potentially sneaking into far southern South
Carolina. This will be the first round of storms capable of
heavy rainfall and isolated damaging winds. Once these storms
depart the area we will begin to focus on the next round to our
northwest. This round of storms will be associated with the more
prominent shortwave trough and approaching cold front. Storms
have already begun to develop across the higher terrain and into
the Midlands this afternoon and will steadily surge southeast
towards the coast through the evening and overnight hours. This
round will likely be our severe weather threat with localized
damaging winds possible especially across areas that do not see
storms during the afternoon across interior South Carolina.
There are some questions on whether or not storms even maintain
severity as they approach given the more stable airmass across
SC, loss of diurnal heating overnight and the fact that we will
become increasingly removed from the parent forcing.

Severe Weather: Looking at the severe potential of these storms,
the environment ahead of any thunderstorms this afternoon
should be conducive for localized damaging winds up to 60 mph.
Temperatures have warmed into the low to mid 90s today and we
expected to see MLCAPE values in excess of 2,000 J/kg. Model
soundings also suggest DCAPE values upwards of 1,000 J/kg
especially across eastern GA, supporting the potential for
damaging wind gusts. There should even be ~20 kts of deep layer
shear across SC which could be enough to support some
organization in the form of multi-cell clusters. Hi-res guidance
has become a little more consistent on the evolution this
afternoon and evening with two main rounds. The first being more
ordinary cells across eastern GA and then the main round coming
out of the SC Midlands this evening. The storms across Georgia
will pose a rather marginal severe threat; however, if the
storms across the Midlands can survive the trek down and persist
into the area they could be the ones to pose a little more
punch. However, they will likely be arriving during the late
evening into the overnight hours leading to lower confidence on
if storms will be able to maintain their intensity into the
Lowlands.


Heavy Rain: Precipitable water values across eastern GA will be
in the 2-2.25" range with PWAT values across SC in the 1.8 to
1.9 range. Given the location of the aforementioned boundary
and this split in PWATs we have trended our heavy rain threat
towards coastal GA vs the SC lowlands. However, thunderstorms
will be very efficient rainfall producers through the afternoon
and evening. We should see hourly rainfall rates of 2+ inches
within the strongest storms which will heighten the locally
heavy rainfall and flash flood risk. The 07/12Z HREF shows
30-50% probabilities of 3 inches of rain in a 3 hour period
across chunk of the area. So, needless to say, the ingredients
for locally heavy rainfall are present and the question is how
quickly do these storms move through and is there potential for
either training or persistent development. There remains some
question as to what areas are at the biggest risk of seeing the
heaviest rainfall. Overall, model guidance has generally shifted
the focus from around the Charleston metro area to be further
south to be more towards the Beaufort and Savannah areas and
this is backed by observations and where the best PWATS and low
level convergence is located. However, parts of South Carolina
could get in on the action this evening as storms move into the
area from the Midlands. The overall risk period will run from
the mid to late afternoon through the late evening hours,
depending on how quickly storms progress.


KEY MESSAGE 3: The potential for coastal flooding will increase
beginning Monday and persist through the middle of the week.

Astronomical tides will continue to rise through the middle of
the week thanks to the lunar perigee which peaks today and the
upcoming new moon (9/11). These factors will push astronomical
tides as high as 6.55 ft MLLW at Charleston Wednesday evening,
setting the stage for coastal flooding potential. A cold front
will push through Sunday night and usher in an extended period
of elevated northeast flow through Tuesday which will drive
increased tidal departures. Coastal flooding will be favored
during the evening high tide cycles at Charleston and the Monday
evening high tide looks like the first one that could exceed
the minor coastal flooding threshold of 7 ft MLLW. While minor
coastal flooding is the most likely scenario, the potential for
moderate coastal flooding (7.5 ft MLLW) will increase with the
Tuesday and Wednesday evening high tides as tidal departures
build within the persistent northeast flow. Coastal Flood
Advisories will likely be needed for Charleston and coastal
Colleton counties.

For the rest of the from Beaufort County south including 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. Therefore, coastal flooding is less likely along this
part of the coast 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 /18Z SUNDAY THROUGH FRIDAY/...
VFR conditions will prevail for most of the afternoon into the
early evening across most of the area. Isolated to scattered
showers and thunderstorms have begun to develop across eastern
GA and should continue to become more scattered to numerous
throughout the afternoon. Temporary restrictions to MVFR or IFR
will be possible within the vicinity of the strongest storms.
This should mainly impact areas around SAV through around 00z.
After 00z, a line of storms should make its way down into the
area bringing temporary reductions to vsbys and ceilings to all
TAF sites from around 04Z to 06Z with the highest chances at
JZI and CHS. These storms will be capable of producing strong
wind gusts, so we have bumped up winds in the PROB30 groups to
include gusts to 30 knots. This could be stronger, but will
depend on if the terminals take a direct hit or not. These
storms should bring at least MVFR conditions with reduced
visibilities due to heavy rain, but at least brief IFR
conditions will be possible as well. Behind these storms, MVFR
ceilings could persist through most of the early morning hours
and at least till around 15Z tomorrow.

Extended Aviation Outlook: Showers and thunderstorms could
again impact the terminals on Monday and Tuesday before coverage
diminishes mid to late week. Breezy northeast winds will also
set up along the coast Monday and Tuesday.

&&

.MARINE...
Tonight: Light onshore flow this afternoon around 10 to 15 knots
will quickly turn northeasterly late tonight when a cold front
drops through from the north. As sunrise Monday approaches, the
surge of northeast flow behind the front will begin to spread in
across the SC waters. Seas should remain in the 2-3 ft range
through the period.

Also of note, thunderstorms are expected to develop inland this
afternoon and evening. These storms could impact the coast and
the coastal waters with strong wind gusts and frequent
lightning.

Monday through Thursday: The surge of northeast flow behind the
cold front will ramp up Monday morning and spread across all
waters through the afternoon. Sustained wind speeds are forecast
to be near 20 knots with gusts around 25 knots across all
waters. These conditions should persist through Tuesday as well.
Small Craft Advisories will almost certainly be needed for all
waters, including Charleston Harbor at times. Seas will ramp up
in response to the northeast surge, with 3-5 feet across much
of the nearshore waters and as high as 6-7 feet across the outer
waters peaking Tuesday. Conditions will begin to improve
quickly Tuesday night into Wednesday as the gradient eventually weakens.


Rip Currents: Persistent and gusty northeast winds and building
seas will support a Moderate Risk of rip currents at all
beaches along the southeast SC and southeast GA coast on Monday
and Tuesday. Depending on trends, a HIGH risk may be needed for
some area beaches on Tuesday.

&&

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

&&

$$

Black/BRS