964
FXUS62 KGSP 281043
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
643 AM EDT Sun Sep 28 2025

.SYNOPSIS...
A stalled frontal boundary will linger along the Carolina coast
today as high pressure briefly builds into the forecast area. A
tropical system will drift northward and approach the South Carolina,
Coast on Monday and Tuesday. It now appears less likely that our
area will experience significant impacts from this system early
next week. The tropical system is expected to move further out
over the Atlantic later in the week as high pressure builds over
our area from the north.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 648 AM EDT Sunday: Other than the usual locally dense
valley fog typical of this time of year, a few patches of fog
were noted elsewhere, but not as bad as locations to our west
and east. Visibility has been variable, so an Advisory will not
be issued. Low temps will remain seasonally mild and on the order
of five degrees above normal.

For the next 24 hours, the mid/upper low/trof will continue to
fill as its axis drifts eastward, leaving behind a weak remnant
over SC by tonight, with an upper pattern that resembles a weak
rex block thanks to an upper anticyclone over the Midwest. Forcing
will be minimal and buoyancy will be poor and shallow, which ought
to place a limit on shower activity outside the mtns. Most of the
CAMs still manage to develop isolated showers over the mtns this
afternoon as a light easterly flow may contribute enough forcing
to go along with differential heating. The model blend might be
a bit deficient in that regard, as it only has a small area with
a slight chance. The precip probs were nudged upward a bit over
the mtns to account for this. Either way, thunderstorms are not
expected to be strong, if they develop at all, and the heavy rain
threat has diminished. Temps will stay fairly close to normal,
probably a degree or two above climo. As for tonight, the weak
remnant low circulation over SC will veer the low level flow around
more easterly across the region, allowing some Atlantic moisture to
move in toward daybreak. A band of low level convergence/isentropic
lift could force some shower activity moving in from the east
by sunrise. The 00Z CAMs are on board and actually drive the
shower activity all the way to the mtns by 12Z Monday. For now,
we will keep the timing of the NBM, which brings the chance of
precip only as far west as a line from Union SC to Lincolnton and
Statesville. The streak of mild overnight temps will continue.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 1:45 AM EDT Sunday: The short-term forecast picks up at 12z on
Monday with what is currently Tropical Depression 9 centered over the
northern Bahamas and just off the coast of southern Florida. At the
same time, Hurricane Humberto is expected to remain further offshore.
Over the next 24 to 48 hrs, TD 9 is expected to gradually track north
and remain just off the SE Coast. Most of the latest model guidance
then has it turn eastward as the period ends early Wednesday. We can
still expect a fair amount of deep-layer wrap-around moisture across
our fcst area on Monday and Tuesday with profiles trending drier by
early Wednesday. Overall, fcst precip amounts on Monday and Tuesday
have been trending lower for most of our CWA. Nonetheless, excessive
rainfall remains a concern over our eastern zones. WPC`s Day 3 and 4
ERO still has most of our CWA in a Marginal Risk for excessive rainfall
with a Slight Risk over a portion of our I-77 Corridor zones. We can
also expect some gusty N to NE winds thru the period, with the highest
gusts likely on Tuesday and Wednesday outside the mountains. At present,
gusts are expected to peak around 30 mph on Tuesday, so any widespread
damage is not anticipated.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 1:25 AM EDT Sunday: The extended forecast picks up at 12z on
Wed with Hurricane Humberto expected to be well off the Atlantic
Coast, while what is currently Tropical Depression 9 is expected
to be located off the SE Coast and beginning to track more eastward.
The system is still fcst to be Hurricane strength at this time.
Over the next few days, most of the current long-range guidance
moves this system further out over the Atlantic as robust sfc high
pressure dives south from Canada and dominates the Eastern Seaboard.
The operational ECMWF still tries to keep the tropical system just
off the Carolina Coast thru the end of the week, but this scenario
still doesn`t appear very likely. Overall, the sensible fcst contin-
ues to trend drier on Wed with little precip now fcst across our CWA
as mid-level drying from the north appears to occur earlier. We can
still expect some gusty N to NE winds on Wed and Thurs, with the pre-
ssure gradient relaxing somewhat by Fri. Otherwise, temperatures
should remain 1 to 2 categories below normal for early October.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Two distinct regimes at daybreak...one with
an IFR/low MVFR ceiling across the I-77 corridor and eastward...and
another over the mountains where fog and low stratus have filled up
the valleys. The restrictions will mainly affect the NC terminals
thru mid-morning, at which time the fog and stratus should mix
out. Won`t rule out popping up a brief MVFR ceiling anywhere
given the amount of low level moisture retained. Wind should
come up from the NE and could be occasionally gusty at KCLT this
afternoon. VFR from 16Z to 18Z onward. For tonight, another shot of
low level moisture will move in from the Atlantic, likely bringing
restrictions to KCLT before daybreak. Other terminals will have
to wait until later in the day.

Outlook: Some flight restrictions can be expected Monday into
Tuesday as a prolonged easterly flow at low levels brings moisture
westward. Most likely this will be in the form of a low cloud
ceiling at MVFR or IFR levels. Beyond that, confidence in precip
is fairly low. Over the mtns, fog and low stratus are possible each
morning, mainly in the mountain valleys and for any locations that
received heavy rainfall the night prior.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...JPT
NEAR TERM...PM
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...PM