Darien, Georgia Weather Forecast Discussion

101
FXUS62 KCHS 291322
AFDCHS
Area Forecast Discussion
National Weather Service Charleston SC
922 AM EDT Mon Sep 29 2025
.SYNOPSIS...
Tropical Storm Imelda will move through the northern Bahamas
today, then northeast away from the Southeast U.S. coast
Tuesday and Wednesday. Cooler high pressure will then build in
from the northwest.
&&
.NEAR TERM /THROUGH TONIGHT/...
29/12z surface analysis showed a coastal front lurking just
offshore with a strengthening Tropical Storm Imelda over the
northern Bahamas. KCLX shows what appears to be a Predecessor
Rain Event (PRE) signature just offshore in the vicinity of the
coastal front. Most of the available guidance this morning
keeps the bulk of this activity offshore, only brushing the
central and upper portions of Charleston County through the
afternoon. While some additional shower activity will develop
west of the PRE signature, it should remain more isolated to
scattered in nature, especially west of I-95. Near term pops
were adjusted locally to reflect current radar and near term
radar trends. Highs from the mid 70s to around 80 look on track
for now.
Tonight: Strengthening Imelda should begin its eastward turn
off the FL coast. Decreasing deep moisture and instability
should reduce coverage of showers to along the coast and the
Atlantic waters tonight. Steady northeast winds around 10 mph
should remain across the forecast area tonight. Low temperatures
are forecast to favor values between 65 to 70 degrees.
&&
.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Tuesday: Tropical cyclone Imelda should continue to move slowly
northward over the western Atlantic while moving on the western
side of a mid-lvl ridge. Thereafter, a trough over the
positioned over the Southeast should cause the system to turn
sharply east-northeastward on Tuesday. This current forecast
keeps the system well offshore of the SC/GA coastline. However,
we still expect some impacts as swells and high surf from both
Humberto and Imelda are expected to produce dangerous marine
conditions and rip currents through the week. Additionally, deep
sub-tropical moisture should bring PWATs +2 inches across the
Eastern Seaboard before drier Canadian high pressure sinks into
the region from the northwest on Wednesday. There should be
ample moisture and forcing for scattered to numerous showers and
thunderstorms to develop near the coastline on Tuesday
afternoon. Continuing the downward trend, rainfall totals have
dropped off quite a bit more with most guidance indicating for
less than 1 inch possible across the eastern half of the
Charleston Tri-County.
Wednesday and Thursday: As Imelda pushes farther away from the
CONUS, strong Canadian high pressure will build in from the
northwest and advect drier air into the region. In response,
PWATs will fall back to near normal and precipitation chances
will be near zero for Wednesday and Thursday. Expect breezy
north-northeasterly winds to prevail as the pressure gradient
remains tight across the region. Ensembles depict below normal
temperatures with highs in the upper 70s to low 80s. Along with
cooler temperatures, dewpoints will drop into the upper 50s to
low 60s making it feel much more fall- like outside.
&&
.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
With this high pressure in place, expect cool an dry weather to
continue through Friday. However, it`s important to note that some
PoPs have been left in the forecast for Friday (mainly along the
coastline) as a weak coastal trough sets up across the Deep South.
Thereafter, this coastal trough tries to move northwestward towards
the region and guidance has been trending towards a wet weekend
ahead.
&&
.AVIATION /13Z MONDAY THROUGH FRIDAY/...
12Z TAFs: The circulation around Imelda will push a coastal
front along the SC to GA coast through the TAF period. Rounds of
showers and possibly isolated thunderstorms will impact the
terminals at times. Forecast soundings and MOS indicates that
cloud bases will likely lower to IFR at times, but remaining
MVFR through the daylight hours. However, this evening, clouds
should lower to IFR after 0Z. Winds should remain from the
northeast through the TAF period around 10 kts. Gusts between
15-20 kts should be common this afternoon.
Extended Aviation Forecast: An extended period of MVFR ceilings is
expected through Tuesday night or Wednesday, along with occasional
vsby reductions due to showers and thunderstorms. Gusty NE winds
also expected through Wednesday.
&&
.MARINE...
The Small Craft Advisory for the Charleston Harbor was pushed
back by a few hours based on current trends. The rest of the
marine forecast is on track.
Today and tonight: The marine zones will remain between
strengthening Imelda to the south and high pressure over the Great
Lakes area. The pressure gradient across the GA and SC waters will
gradually increase through the near term. Northeast winds should
gradually strengthen to 20 to 25 kts with gusts into the low 30s by
tonight. In addition, this afternoon mixing should result in some
momentum transfer across the CHS Harbor, yielding gusts around 25
kts. Swell sourced from major hurricane Humberto and strengthening
Imelda will build across the marine zones through today and tonight.
By late tonight, seas should range from 6 to 12 ft. Small Craft
Advisories are in effect for all marine zones through the near term.
Tuesday through Saturday: Breezy north-northeasterly winds at 20 to
25 kt with gusts up to 30-33 kt will likely hold through the latter
part of the week as TS Imelda and Hurricane Humberto meander over
the western Atlantic and a strong high pressure builds down from
Canada allowing for the pressure gradient to tighten up across the
local waters. Additionally, swell from TS 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 12 ft in the outer Georgia waters
(possibly 14-15 ft) on Tuesday through Thursday. By Friday, the
swell should begin to taper off some, but seas will remain quite
volatile 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 w/ the Charleston Harbor SCA likely
ending sooner) due the combination of high winds and seas.
Rip Currents: A High Risk of rip currents is expected today and
Tuesday at all beaches due to large, long-period swells and strong
winds.
&&
.TIDES/COASTAL FLOODING...
Strengthening north-northeasterly winds this week will result in an
increase in tidal anomalies. There is quite a bit of uncertainty
regarding how large the positive anomaly will be given that the wind
directions could be more north-northeasterly rather than
northeasterly. There is a fine line between which wind direction
causes for the greatest Ekman forcing along the SC/GA coastline.
However, the latest forecast from Imelda favors a more
northerly fetch, thus in this case, the anomaly may not get much
higher than +1.6 ft. As of recent, the only flooding we are
depicting is minor coastal flooding at Charleston on Wednesday
Afternoon with a high tide of 7.2 ft.
A High Surf Advisory has been issued for southeast Georgia and
southeast South Carolina beaches this evening until the end of the
week due to +5 ft breaking waves.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents until 8 PM EDT this evening for GAZ117-
     119-139-141.
     High Surf Advisory from 8 PM this evening to 8 AM EDT Saturday
     for GAZ117-119-139-141.
SC...High Risk for Rip Currents until 8 PM EDT this evening for
     SCZ048>051.
     High Surf Advisory from 8 PM this evening to 8 AM EDT Saturday
     for SCZ048>051.
MARINE...Small Craft Advisory from 5 PM this afternoon to 2 AM EDT
     Wednesday for AMZ330.
     Small Craft Advisory until 9 AM EDT Saturday for AMZ350.
     Small Craft Advisory until 8 PM EDT Sunday for AMZ352-354-374.
&&
$$

NWS CHS Office Area Forecast Discussion