259
FXUS62 KCHS 301809
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
209 PM EDT Tue Sep 30 2025

.SYNOPSIS...
Hurricane Imelda will move northeast away from the Southeast
U.S. coast through Wednesday. High pressure will then prevail
through the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Hurricane Imelda located well offshore of the Southeast U.S.
will continue to move the northeast into Wednesday. Drier air
noted over the Delmarva and the Virginia Tidewater this
afternoon is forecast to drop quickly south and expand over the
region tonight which will bring a change in airmass over the
region. Light rain showers this evening will end by late
afternoon/early evening as the drier air begins to advect south.
Cloud ceilings will steadily lift with high clouds mainly
dominating for the overnight period. Lows tonight will range
from the lower 60s well inland to around 70 at the beaches.
Breezy conditions along the beaches may diminish a bit overnight
as winds back more northerly.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
What is now Hurricane Imelda will be pushing out to sea by
Wednesday morning, with drier air being advected across the
region leading to a dry forecast. In fact, dew points in the
upper 50s to lower 60s will be common before an afternoon sea-
breeze attempts to push ashore, possibly bringing dew points
into the mid 60s alongshore. Without all of the moisture to heat
up, h850 temps of near 15 deg C will bring the region back into
the lower to mid 80s, accompanied by breezy northeast winds.

Overnight into Thursday, a closed off upper level low opens up
into a trough as it approaches the southern portion of the east
coast, with a surface high pressure expanding along the northern
portion of the east coast. Cold-air advection at the h850 level
will keep afternoon highs on the cooler side in the mid 70s to
lower 80s, so it`ll certainly feel like fall out there!
Unfortunately the surface pressure gradient will remain fairly
consistent, keeping northeasterly winds on the breezier side
with gusts into the lower to mid 20s. Shortwaves from the
aforementioned trough begin to move across our Georgia coast
during the late afternoon and evening hours, so can`t rule out a
few showers or even a thunderstorm, with chances expanding
northwards up along the South Carolina coast by sunrise Friday.

Overnight into Friday morning, the region looks to firmly be in
a surface pressure wedging scenario, keeping us on the cooler
side of normal with highs in the upper 70s to lower 80s. Breezy
winds will also be continuing, gusting into the teens to lower
20s throughout the day.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
Surface high pressure wedging is expected to continue into the
weekend, though the high pressure itself will be shifting
eastwards into the Atlantic waters. This will continue our
similar conditions since Thursday, though winds will be slightly
more east than northeastwards. Given the slight shift in wind
direction, it does tend to allow for a sea-breeze to form, which
will aid in creating scattered showers and thunderstorms during
the afternoon hours on Saturday and again on Sunday. Given
little change in the pattern Saturday and Sunday, training
thunderstorms (thunderstorms going over the same location) may
be capable of leading to rainfall totals adding up to 2+ inches.
While this alone won`t lead to any minor flooding concerns, if
a local area did see a stronger storm that is able to produce
higher rainfall, minor flooding may be possible, which WPC
agrees with and has a Marginal risk (level 1 out of 4) for
excessive rainfall.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
30/18z TAF Discussion:
KCHS/KJZI/KSAV: MVFR cigs will gradually give way to VFR by
late afternoon/early evening as drier air to the north pushes
south. VFR will then prevail through the end of the 18z TAF
period. Gusty winds with gusts near 20 kt will diminish by early
evening.

Extended Aviation Forecast: No flight restrictions expected
Wednesday through Thursday morning. Brief flight restrictions
are possible Thursday afternoon into the overnight hours Friday,
though otherwise VFR conditions are expected. Chances for
afternoon showers/thunderstorms chances continue Saturday and
Sunday.

&&

.MARINE...
Tonight: Hazardous marine conditions are in place across the
waters this afternoon with north to northeast of 20-25 kt with
gusts to 30 kt prevailing. There have been some local wind
minimums observed at times today, which have been hard to both
diagnose and depict in the gridded forecasts. Overall, 20-25 kt
with gusts to 30 kt should prevail through the night as winds
turn more northerly all areas overnight. Seas will reach 6-10 ft
across the nearshore waters and 10-13 ft over the Georgia
offshore waters. Small Craft Advisories will remain in place for
all legs through tonight. For the Charleston Harbor, winds will
remain rather marginal for an advisory, but the advisory was
maintained for 15-20 kt with gusts to 25 kt and waves 1-2 ft.

Wednesday through Sunday: Breezy north-northeasterly winds at
20 to 25 kt with gusts up to 30-33 kt will likely hold through
the middle of the week, given the increased surface pressure
gradient from Hurricanes Imelda and Humberto over the Atlantic
and a surface high pressure building down from Canada. In
addition, swells from Imelda with long-period swell from
Humberto will continue to build into the local waters through
the weekend causing seas to slowly increase to 8 to 10 ft in the
nearshore waters, and 10 to 11 ft in the outer Georgia waters
on Wednesday and Thursday. By Friday, the swell should begin to
taper off some, but seas will remain quite volatile into the
weekend with waves +6 ft across all marine zones. Therefore,
Small Craft Advisories (SCAs) have been issued for all marine
zones through the end of the week, though the Charleston Harbor
will likely need to be ended sooner) due the combination of high
winds and seas.


Rip Currents/High Surf:
Tonight: Local surf shops and public reports show breakers at
Folly Beach have been 4-5 ft with sets as high as 6-7 ft at
times over at the Wash Out. NWPS wave breaking guidance suggest
breaking waves may increase by about one more foot through
tonight. The High Surf Advisory and High Rip Current Risk were
maintained.

Tuesday through Saturday:
A High Risk of rip currents is expected into Thursday at all
beaches due to large, long-period swells and strong winds. In
addition, large breaking waves of 5+ feet are expected through
much of the week and a High Surf Advisory remains in effect.

&&

.TIDES/COASTAL FLOODING...
The Coastal Flood Advisory for Charleston and Coastal Colleton
Counties has been cancelled. Northerly winds should keep tidal
departures less than 1.5 ft at high tide, which would tide
levels below the minor flood threshold of 7.0 ft in the
Charleston Harbor. As astronomical tides increase later this
week, the risk for minor coastal flooding will persist for
mainly Charleston and Coastal Colleton Counties.

Heading into this weekend and early next week, astronomical
tides will increase due to the upcoming Full Moon (Oct 7) and
Perigee (Oct 8). This in combination with the anticipation of
continued northeasterly flow will cause the possibility of
coastal flooding to become more likely along the entire
coastline, including both Downtown Charleston and Fort Pulaski.
Saltwater inundation could then occur during both the morning
and evening high tide cycles during this time. Although there is
considerable uncertainty this far out, persistent favorable
winds have the potential to produce up to major coastal
flooding.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents through Wednesday evening for GAZ117-119-
     139-141.
     High Surf Advisory until 8 AM EDT Saturday for GAZ117-119-139-
     141.
SC...High Risk for Rip Currents through Wednesday evening for SCZ048>051.
     High Surf Advisory until 8 AM EDT Saturday for SCZ048>051.
MARINE...Small Craft Advisory until 2 AM EDT Wednesday for AMZ330.
     Small Craft Advisory until 6 AM EDT Monday for AMZ350-352-354-
     374.

&&

$$