501
FXUS62 KGSP 180544
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
144 AM EDT Sat Oct 18 2025

.SYNOPSIS...
Dry conditions continue today, before a cold front arrives
on Sunday, bringing showers and a few thunderstorms with it.
Dry and cool conditions return next week, lingering through at
least next Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 140 AM Saturday: Cirrus is moving east of the area and
mountain valley fog is developing. Can`t rule out some patchy fog
elsewhere. Fog should dissipate shortly after daybreak.

An upper ridge axis and surface high pressure over the area move
east today as a trough and associated cold front approach from the
west. Generally clear skies, southwesterly flow, and rising
thickness values will lead to highs around 10 degrees above normal.
Low end gusty winds expected during the afternoon. Low level
moisture increases overnight on the southwesterly flow. Showers
ahead of the front will be approaching the area late tonight and may
move into the mountains before daybreak, but the bulk of the precip
will be after. Lows will be around 10 degrees above normal with the
warm air mass, increasing clouds, and southwesterly flow in place.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 1226 AM EDT Saturday...

Key Messages:

1) Conditional, low-end severe potential remains in place for
Sunday with a passing cold front, but depends on several factors
that aren`t yet clear.

2) At least scattered showers develop on Sunday, but confidence
is much lower on how much, if any, thunder occurs.

3) Breezy conditions persist behind the front, and temperatures
cool significantly into Monday.

The primary forecast challenge in the short term remains the
potential for strong to severe convection on Sunday afternoon.
By daybreak Sunday, a potent, negatively-tilted z500 trough axis
will be located somewhere over the west-central Tennessee Valley,
extending north into Illinois and Wisconsin.  Its attendant cold
front will be located farther east...potentially as far as eastern
Tennessee based on surface theta-e analysis...and the latest CAM
runs depict fairly anemic convection along it, about what you`d
expect at the diurnal minimum.  As the day progresses...it`s really
going to boil down to how the parameter space evolves over the
western Carolinas.  Shear won`t be an issue - the latest RAP and
HRRR analyses still depict upwards of 60kts of deep layer shear
- but instability remains a potentially-major limiting factor.
This evening`s RAP runs are intent on depicting a warm layer near
700mb, which severely constrains the amount of CAPE available
to developing updrafts.  The most aggressive scenario would
paint the SC Upstate with 300-500 J/kg sbCAPE, more than enough
for a legitimate severe threat; the more likely scenario still
looks like 100-250 J/kg...and even then, given the timing of the
front, this instability may well not be realized until the front
is partway across the area.  This is still certainly enough to
drive some showers and a few embedded thunderstorms, which may
even become organized by virtue of the shear; however, that pesky
warm layer is going to do a number on any updrafts, limiting both
their strength and longevity.  Accordingly, the latest HRRR and
NAMnest both depict pretty unimpressive development over most of
the CWA early Sunday...before some redevelopment takes place over
the I-77 corridor in the afternoon, as daytime instability starts
ramping up before the system moves east of our CWA.

The remainder of the forecast is less contentious.  With the front
crossing the area during the day Sunday, it`s likely that at least
the western 2/3 of the CWA will get a blast of postfrontal air
mass before peak heating...and so highs could land in the upper 60s
or lower 70s.  Farther east, especially across the I-77 corridor,
the front won`t quite clear the area in time to limit highs...so
these areas could see temps climb into at least the mid-70s.
Behind the front Sunday night, a brief slug of CAA should develop,
and temperatures everywhere will drop into the low-/mid-40s,
with the higher elevations still expected to see lows in the 30s.
A steady NW wind is expected everywhere...and the boundary layer
tentatively looks to stay mixed enough to support gusts into the
low teens into early Monday.  They`ll drop off pretty sharply after
daybreak, though, and as the new air mass settles into the region,
the remainder of the day should be sunny and quiet, with highs in
the upper 60s.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 1241 AM EDT Saturday...

Key Messages:

1) Dry and cool conditions persist for most of the week.

2) A cold front crosses the region on Wednesday, but produces
little to no rainfall.

Still expecting a progressive, but mostly uneventful synoptic
pattern to develop through the remainder of next week.  The next
upper disturbance - probably a closed low - will be churning over
the Great Lakes by Tuesday morning, but although it`ll quickly march
eastward, height falls over the Carolinas look to be minimal as the
upper low migrates northeastward through Wednesday.  The associated
surface cold front is finally being handled consistently in today`s
LREF cycle, with at least 75% of the long-range ensembles bringing
the front east of I-77 by mid-day Wednesday.  With little to no
moisture return ahead of it, though, there`s still a pretty good
consensus that the front will be dry...doing little more than
reinforcing below-normal temperatures through late in the week.

A few of the long-range ensembles - particularly those belonging to
the GEFS - have begun keying on another upper disturbance developing
off the coast of Baja California mid-week, translating across the
southern CONUS through Thursday and Friday, and arriving in the
Carolinas near the end of the 7-day forecast period.  It`s too soon
to say what, if any, impacts may be associated with this system,
but if guidance remains consistent, it could be our next chance
for rainfall.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: With cirrus moving east of the area, mountain
valley fog is forming. The question, as usual, will the fog develop
at KAVL. For now, have gone with a TEMPO for MVFR vsby near
daybreak. All other terminals will stay VFR with diminishing cirrus
and light S to SW wind. Wind speeds pick up during the day with low
end gusts developing for all but KAVL and KHKY for the afternoon.
Gusts diminish by evening, but speeds remain slightly elevated. Low
VFR clouds move in overnight, with any precip after this TAF period.

Outlook: A cold front may bring showers and associated restrictions
Sunday along with breezy conditions. Dry conditions return on
Monday. A dry cold front may bring breezy conditions again on
Tuesday lingering into Wednesday.

&&

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

&&

$$

SYNOPSIS...MPR
NEAR TERM...RWH
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...RWH