815
FXUS62 KCHS 041817
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
217 PM EDT Sat Oct 4 2025

.SYNOPSIS...
Strong high pressure will extend across the region through the
weekend and into early next week. A strong cold front will
likely cross the area later next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Tonight: The parent surface high across the Mid Atlantic will
become aligned more east/west and centered more to the northeast
of the area, allowing the low-level flow to take on a more
easterly component. The result is that the coastal trough will
push more to the coast and allow for shower activity to spread
more inland. This is well supported by the suite of hi-res
models as well as the HREF, with all showing an increasing
coverage area pushing into the coast and inland around midnight
and through the late night hours. There are some differences
with where the peak coverage will occur, but there is general
agreement with it occurring between the central Charleston
County coast down to the Chatham County coast. There could be
some decent rainfall amounts, generally between 0.25-0.50 inches
through sunrise. Furthermore, the HREF indicates some 50%
probabilities of amounts around an inch in the area between
Charleston and Savannah. Will increase rain chances to account
for this in the forecast. Expect another mild night with lows in
the mid to upper 60s for most of the area.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
Upper level ridge holds tight across the eastern CONUS Sunday
as sfc high pressure wobbles eastward across the Carolinas. An
inverted trough will also continue to linger along the coast
during this time, resulting in continued chances for showers and
storms. As noted in the previous discussion, significant
forcing with this feature remains pretty limited. Despite there
being a decent push of subtropical moisture, latest CAMs
continue to shift the axis of higher rainfall just south of our
area. Nonetheless, still expect to see some activity here during
the afternoon and evening, with the better chances for seeing
showers generally along and south of Beaufort. Accumulations in
these areas through Monday look to range from 0.5 to 1.5 inch,
with perhaps a few isolated pockets of 2 inches.

Expect largely dry conditions to prevail Tuesday as the sfc
ridge axis slides overhead. This will allow for a brief reprieve
in breezy northeasterly winds - especially along the coast,
with highs forecast to rise into the low to mid 80s under mostly
sunny skies.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
H5 heights fall modestly Wednesday as a shortwave passes north
of the area, then more quickly Thursday into Friday as stronger
troughing digs across the Missouri Valley and a shortwave
crosses the Southeast. At the surface, strong high pressure
building quickly over the Northeast will force a backdoor cold
front down the eastern seaboard, likely crossing our area very
early Thursday. In terms of rainfall, overall low to mid level
moisture remains fairly meager, which should keep accumulations
on the lighter side with any coastal shower that occurs with
FROPA.

Gusty NE winds return Thursday into Friday behind the front -
25th to 75th percentile reflecting a most likely wind speed
along the coast of around 20-30 mph - to end the workweek,
which, in addition to already elevated tide levels, could bring
a period of very impactful tidal flooding to end the week. See
coastal flooding section for more.

Otherwise, model certainty decreases heading into next week, as
guidance diverges on how the aforementioned front will
progress. While some guidance suggest the boundary will stay
outside of our area, a few solutions do have it moving back
northward, causing unsettled conditions to return. Certainly
something to monitor in the coming days!

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
The 18z TAF period begins with VFR conditions at KCHS, KJZI,
and KSAV. VFR conditions should prevail through the evening as
well. However, beginning as early as around midnight, a notable
increase in shower coverage is expected to reach the coast and
shift onshore. This should bring showers, reduced visibilities,
and lowering ceilings into the TAF sites. This activity should
generally peak in the 06-12z time period with periodic MVFR
conditions with even a chance of seeing brief periods of IFR.
This shower activity should shift inland and dissipate by around
mid morning and VFR should return for the end of the TAF
period.

Extended Aviation Forecast: The risk for restrictions from
showers/tstms Sunday and Monday continues to decrease, though at
least brief restrictions remain possible, especially at SAV.
Otherwise, no significant aviation impacts expected.

&&

.MARINE...
Tonight: Northeast winds will prevail early this evening,
followed by a turn to become more easterly through the
overnight. Wind speeds should mostly stay in the 15-20 knot
range, with occasional gusts to 25 knots, especially beyond 20
nm. Seas will remain elevated with 4- 6 feet across the
nearshore waters and 5-7 feet in the outer waters. Small Craft
Advisories remain in effect for all local waters outside
Charleston Harbor.

Sunday Onward: Very long fetch easterly winds will bring
persistent medium period swell across the waters, with some
underlying, but much smaller, longer period swell through early
week as well. The swell will peak Sunday night into Monday with
wave heights reaching 6-9 ft offshore, before only gradually
subsiding through midweek, when breezy NE winds will begin to
ease as well.

Rip Currents: A high risk of rip currents will continue through
Monday in primarily medium period E to NE swells.

&&

.TIDES/COASTAL FLOODING...
Tidal departures remain quite high as we move towards the early
evening high tide cycle. In fact, departures continue to trend
slightly higher than guidance so we have increased the forecast
a tenth at both Charleston (7.5 ft MLLW) and at Fort Pulaski
(9.5 ft MLLW). Therefore, the Coastal Flood Advisory is now in
effect for the entire coast.

Astronomical tides will continue to increased through next week
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 by the latter part of next
week.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents until 8 PM EDT this evening for GAZ117-
     119-139-141.
     Coastal Flood Advisory from 5 PM this afternoon to 9 PM EDT
     this evening for GAZ117-119-139-141.
SC...High Risk for Rip Currents until 8 PM EDT this evening for
     SCZ048>051.
     Coastal Flood Advisory from 5 PM this afternoon to 9 PM EDT
     this evening for SCZ048>051.
MARINE...Small Craft Advisory until 2 PM EDT Tuesday for AMZ350-352-354.
     Small Craft Advisory until 6 AM EDT Wednesday for AMZ374.

&&

$$

NEAR TERM...BSH
SHORT TERM...SST
LONG TERM...SST
AVIATION...BSH/SST
MARINE...BSH/SST