Osborn, South Carolina Weather Forecast Discussion

790
FXUS62 KCHS 021718
AFDCHS
Area Forecast Discussion
National Weather Service Charleston SC
118 PM EDT Thu Oct 2 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 cold front may approach the region in the middle of
next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Feeling quite fall-like out there, with temperatures in the lower to
upper 70s, dewpoints in the 50s inland to 60s along the coast, and a
gusty north-northeast wind. This is occurring as a ~1030mb high
pressure wedge remains centered on the northeast coast, with an
area of low pressure in the far southwest portion of the Gulf,
leading to a high surface pressure gradient across the region.
This will lead to a dry forecast for most, though some weak
isentropic lift may result in some very scattered showers in our
far southerneastern Georgia counties along the coast. There is
a roughly 20% chance for these starting early this evening, with
chances expanding up the rest of the Georgia coast into the
early overnight hours. Any amounts are expected to remain light
at under a quarter of an inch. Overnight temperatures drop
towards the upper 50s inland to mid 60s along the coast, with
breezy winds continuing.
Aloft, h500 heights remain fairly consistent across our area, though
weak troughing is expected to occur across the Gulf Stream. NHC
highlights this area within the trough between Florida and the
Bahamas with a 10% of formation over the next 48 hours.
&&
.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Friday and Saturday: The pseudo Rex configuration of the upper air
pattern across the eastern CONUS will gradually translate to the
upper level high settling offshore of the North Carolina Outer Banks
with the upper low over the northwest Gulf/Louisiana coast through
the weekend. The strong inland wedge that has been in place for the
past several days will gradually weaken as the confluent flow over
the Northeast U.S. diminishes and unlocks the parent high over New
England. This will allow the parent high to sink to the
south/southeast, ending up offshore of the Virginia Tidewater by
Sunday. Until this occurs, a stiff northeast low-level flow will
persist with subtle coastal trough lurking just offshore. Models are
still likely overdeveloping shower activity over the Atlantic
associated with an extensive marine-based stratocumulus field left
in the wake of Imelda; a known bias in the various model suites,
especially in the cool/cold season. At least a downward recent has
been noted. Still expect some degree of shower activity to impact
the beaches, but most of any activity that forms will be redirected
into northeast Florida and possibly far southern coastal Georgia.
Seasonable temperatures will continue with highs peaking in the
upper 70s/lower 80s both afternoons with lows Saturday morning
ranging from the mid 60s well inland to the lower-mid 70s at the
beaches. A pinched gradient associated with the inland wedge will
keep breezy conditions in place at the beaches both days.
Sunday: An increasingly moist flow will develop across the area by
Sunday as the region becomes pinned between the upper high off of
Cape Hatteras and the upper low over the far northwest Gulf.
Guidance is pretty similar in showing a weak impulse, possibly even
a subtle surface low, developing near a stalled front over the
Florida peninsula in response to band of vorticity passing through
aloft. As this system moves into the northeast Gulf, the northern
fringe of what looks to be a fairly large rain shield will begin to
spread into Southeast South Carolina and Southeast Georgia. There is
a lot of uncertainty here as much will depend on how strong any
disturbance to the south becomes with the GFS and ECMWF ensemble
members supporting a much weaker system compared to their
operational counterparts. Even if the system ends up much weaker,
the same band of vorticity moving across the Florida peninsula will
propagate into the Southeast U.S. and interact with the lingering
coastal trough offshore to also aid in rain production. Bottom line,
rain chances will be on the increase through Sunday, but the
associated QPF is highly uncertain. PWATs are forecast to increase
to 2-2.25", so there will be a risk for conditional risk for
locally heavy rainfall possibly some minor flooding, mainly in low-
lying and poor drainage areas. Highs will warm in the upper
70s/lower 80s.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The risk for rainfall will persist into the middle of next week as
moist conditions linger ahead of an approaching cold front.
Confidence how much convection will occur in the warm sector is a
bit uncertain with upper pattern favoring a pretty steady stream of
hard-to-time impulses passing through in the southerly flow aloft.
NBM pops were generally favored, showing chance to likely pops
Monday with slight chance to chance pops Tuesday into Wednesday.
Highs each day will warm into the lower-mid 80s with overnight lows
in the mid-upper 60s inland to the 70s at the coast.
&&
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
18Z TAFs: A pinched surface pressure gradient is resulting in breezy
northeasterly winds, gusting into the teens to lower 20s. There is a
low chance (~20%) for an isolated showers or storm to form this
evening/overnight along the southeastern Georgia coast, but did
not include mention at any of the TAF sites. While VFR
conditions are expected to prevail into the morning hours, some
guidance is hinting at an MVFR cloud deck forming with those
aforementioned showers over the ocean and advecting those onto
land. Not sold on that solution, so have kept VFR conditions
going.
Extended Aviation Forecast: There are no high confidence concerns.
The risk for restrictions from showers/tstms will increase this
weekend into early next week for all terminals.
&&
.MARINE...
Through Tonight: A pinched surface pressure gradient is resulting in
breezy northeasterly winds, as of 1 PM sustained in the mid to upper
20s with gusts in the upper 20s to lower 30s. For the rest of the
afternoon and into the evening hours, expecting similar if not a
touch stronger winds for the rest of the day and into the overnight
hours. Did consider upgrading to a Gale warning, but looking at the
various models it`s not looking like we would reach the sustained
criteria, and the gust criteria would be rather inconsistent and not
reaching the duration criteria. The last swells from Imelda will
remain across the marine zones through the near term, peaking
today/tonight between 6 to 11 ft. Small Craft Advisories are in
effect for all marine zones.
Friday through Tuesday: Pinched gradient conditions associated with
the inland wedge will keep northeast winds 20-25 kt with gusts to 30
kt in place through the weekend. The gradient will begin to relax
Monday into Tuesday as a warm front shifts north and winds become
more east to southeast. The combination of both winds and seas will
keep solid Small Craft Advisory conditions in place through Tuesday
for most legs. Peak seas will average 5-8 ft nearshore waters and 8-
11 ft over the Georgia offshore waters through the weekend, then
slowly subside.
Rip Currents/High Surf: A high risk rip currents will continue into
Saturday. NWPS breaking wave guidance still shows breakers at 4-6 ft
with sets up to 7 ft holding through Saturday morning. The High Surf
Advisory remains in place.
&&
.TIDES/COASTAL FLOODING...
As astronomical tides increase this week, the risk for minor coastal
flooding will increase for Charleston and Coastal Colleton Counties
during the afternoon high tide cycle. A Coastal Flood Advisory
has been issued for 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 Friday 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 Friday evening for SCZ048>051.
     High Surf Advisory until 8 AM EDT Saturday for SCZ048>051.
     Coastal Flood Advisory until 7 PM EDT this evening for SCZ049-
     050.
MARINE...Small Craft Advisory until 2 AM EDT Friday for AMZ330.
     Small Craft Advisory until 2 PM EDT Tuesday for AMZ350-352-354.
     Small Craft Advisory until 6 AM EDT Wednesday for AMZ374.
&&
$$
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...

NWS CHS Office Area Forecast Discussion