105
FXUS62 KCHS 031817
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
217 PM EDT Fri Oct 3 2025

.SYNOPSIS...
A strong high pressure will extend across the region into the
weekend, with rain chances increasing on Sunday into early next
week. A strong cold front will likely cross the area later next
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Tonight: Overall, the pattern will remain the same with high
pressure still centered to the north stretching across the Mid
Atlantic region. This will maintain persistent northeast flow
across the area with a subtle coastal trough positioned
offshore. There are some indications in the hi-res guidance that
this trough will shift a bit closer to shore overnight,
potentially allowing shower activity to brush more of the coast
overnight. Still, the bulk of the shower activity should remain
over the coastal waters and the trajectory of the flow will
highlight the GA coast as having the best rain chances through
the overnight. Rainfall amounts along the GA coast should be a
few hundredths in most areas, though the further south you go
closer to the Altamaha there could be some amounts upwards of
one or two tenths. Temperatures aren`t expected to be quite as
cool as they were the previous night, with lows more in the low
to mid 60s for most locations.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
Upper level ridge holds tight across the eastern CONUS this
weekend, as a sfc high pressure gradually pushes eastward across
North Carolina into the Atlantic. As noted in the previous
discussion, an inverted coastal trough will keep NE to E flow in
place for much of Saturday. While forcing remains quite meager,
latest CAMs continue to support chances for showers offshore
during the afternoon and evening, with perhaps a few pushing
inland across southeastern Georgia. Nonetheless, with a decent
amount of dry air to work with in the lower levels, not
expecting to see much in the way of significant rainfall.

The inverted trough continues to linger along the coast Sunday,
which combined with increasing 850mb moisture and an advancing
coastal low will result in a more unsettled pattern heading into
Monday. That being said, latest guidance has started to shift
the overall axis of heavy rainfall a bit southward, where the
better instability and vorticity exist. Could certainly still
see things shift over the next few forecast cycles, but for now,
latest NBM run has decreased PoPs across our area both Sunday
and Monday. Now have PoPs ranging between 20 to 60 percent
across our area, with the greatest threat (50-60% PoPs) south of
Savannah. Total Sunday and Monday rainfall accumulations of 2
to 4 inches are well within reason for coastal areas from
Beaufort County southward, including the Savannah Metro area,
with localized/reasonable worst case scenario amounts reach up
to 5 inches.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Upper ridging builds modestly Tuesday before a series of
shortwaves potentially move through mid-to-late next week. At
the surface, high pressure shifts over Bermuda Tuesday, ridging
into our area from the west into midweek, with only low-end
precip chances. Then, by late week, very strong high pressure
building over the Northeast is expected to force a strong
backdoor cold front down the eastern seaboard as a CAD-like
setup takes hold Thursday into Friday. The most impactful aspect
of this forecast could end up being the good agreement on NE
winds - 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 level, could bring
a period of very impactful tidal flooding. See coastal flooding
section for more.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
The 18z TAF period begins with VFR conditions in place at KCHS,
KJZI, and KSAV. Overall, VFR conditions are expected to prevail
through the period. We will continue to see occasional shower
activity push onshore along the GA coast south of KSAV into the
overnight. However, by tomorrow morning we could see a shift in
this activity further north, potentially even up the SC coast.
So, isolated passing showers can be ruled out near the end of
the period. Stratocumulus will push onshore as well, with bases
mostly in the 3-4 kft range. This cloud cover should mostly
remain scattered, keeping conditions VFR. Wind gusts into the
15-20 knot range will be possible through the afternoon, and
could again pick up by mid to late morning on Saturday.

Extended Aviation Forecast: The risk for restrictions from
showers/tstms will increase this weekend into early next week
for all terminals. Otherwise, no significant aviation impacts
expected.

&&

.MARINE...
Tonight: High pressure will remain centered to the north which
will maintain persistent northeast flow within a tight pressure
gradient. This will keep elevated winds and seas going through
the overnight. Winds should peak in the evening with speeds
expected to be 15-25 knots with frequent gusts into the 25-30
knot range. These speeds could diminish a bit through the late
night hours as the gradient relaxes. Within Charleston Harbor,
winds should mostly top out in the 15-20 knot range. Seas will
peak in the evening with 4-7 ft common across the nearshore
waters and 6-9 ft in the outer waters. Then by very late
tonight, seas could drop off to be 4-6 ft in the nearshore
waters and 5-8 ft in the outer waters. Regardless, conditions
will remain supportive of Small Craft Advisories for all waters
outside Charleston Harbor.

Saturday through Tuesday: High pressure ridging inland and
inverted coastal troughing off the coast continue breezy N to NE
winds through the weekend. Winds trend more E early next week
as high pressure moves further off the Mid-Atlantic coast, but a
very long eastern fetch is likely to keep hazardous seas in
place into mid-week despite winds trending more moderate.

Rip Currents: A high risk of rip currents will continue through
Sunday in primarily medium period E to NE swells. High Surf
Advisory remains in place through Saturday, though lower
confidence in 6+ ft breaking waves still exist Saturday night
into Sunday. Will continue to monitor trends and extend
headlines as needed.

&&

.TIDES/COASTAL FLOODING...
A Coastal Flood Advisory has been issued for the upcoming
afternoon high tide at Charleston. Tidal departures remain high
and with the astronomical high tide being at 6.05 ft MLLW, we
should get up into a range of 7.1-7.3 ft MLLW.

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
by the latter part of next week.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents through Saturday evening for GAZ117-119-
     139-141.
     High Surf Advisory until 8 PM EDT Saturday for GAZ117-119-139-
     141.
SC...High Risk for Rip Currents through Saturday evening for SCZ048>051.
     High Surf Advisory until 8 PM EDT Saturday for SCZ048>051.
     Coastal Flood Advisory until 8 PM EDT this evening for SCZ049-
     050.
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