Area Forecast Discussion
Issued by NWS Greer, SC

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439
FXUS62 KGSP 012313
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
713 PM EDT Wed Oct 1 2025

.SYNOPSIS...
Dry high pressure ridging down from the northeast will control
our weather through the end of the week, bringing cooler than
normal temperatures for Thursday and Friday.  As the center of
high pressure moves offshore, temperatures return to near normal
for the weekend.  Moisture increases Sunday through early next week.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 710 PM Wednesday: Patchy cirrus, and even some patchy
stratocu, continue to stream across the area this evening. The
stratocu should dissipate, but return to the Blue Ridge and portions
of the mountains as moisture trapped under a subsidence inversion
moves in on easterly upslope flow. Winds have diminished as
expected. Lows look on track as does the rest of the forecast.

Otherwise, a quiet forecast continues across the region as upper
troughing slides offshore and an upstream ridge over the Mississippi
Valley shifts east into the Appalachians overnight into tomorrow.
Surface high pressure over the southern end of Hudson Bay is
forecast to drop south into New England by tomorrow which will send
a reinforcing shot of cool and dry air into the area tonight. Ahead
of this cooler air, temperatures will remain warm today in the upper
70s to low 80s. For tonight, an easterly upslope component to the
flow may foster the development of clouds along the escarpment with
higher elevations seeing foggy conditions in the clouds, but
otherwise a continuation of benign weather. The forecast turns
cooler tomorrow as 850mb temperatures fall with highs in the low to
mid 70s. 15-20kts of flow within the mixed boundary layer will
support a continuation of occasionally gusty winds both this
afternoon and again tomorrow afternoon.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 1210 PM Wed: Cold-air damming is likely to be established prior
to the start of the period Thu evening. Although the damming high
will shift southward and weaken slightly over the subsequent 48
hours, CAD should persist. Deep subsidence should keep skies
virtually clear aside from the possibility of shallow nocturnal
stratus developing via onshore low-level flow. That introduces a
little bit of uncertainty into overnight temp forecasts, but the
moist layer looks too shallow to expect any more than single-digit
(and therefore unmentionably low) PoPs even where clouds do form.
Cloud cover generally looks more likely Fri night into Sat when flow
turns more SE`ly following the southward shift of the high. The NAM
does produce a few sprinkles around that time, evidently via very
shallow instability under the wedge inversion, but that sort of thing
tends to be overdone by the NAM, so we`re not putting much value in
that at this time.

Thursday night temps will trend a few degrees lower than the previous
night, with good radiational cooling conditions assuming the cloud
cover remains patchy or limited to near daybreak. However, values
actually end up only 2-4 degrees below normal at most. Lower 40s or
even upper 30s are possible in the higher mountains, but probably too
warm for frost even there. Temperatures look to trend slightly warmer
Fri night as airmass modifies, even assuming cloud cover doesn`t
materialize. Most areas will see maxes Saturday rise back to normal
if not a degree or two above.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 100 PM Wed: No appreciable change in the general expectation
Saturday night thru early next week. Eastward migration of upper
ridge and offshore migration of the sfc high together are poised to
permit return flow and some moisture flux aloft. A marked increase in
cloud cover is expected Saturday night into Sunday with precip
chances rising to a mentionable level (20-30%) by Sunday night in
areas southeast of the Blue Ridge Escarpment, slightly more of the
area Monday, and in all of the CWA by Tuesday afternoon. Support for
CAD will diminish as the sfc high moves offshore, but as clouds and
possibly light precip increase--increasing the likelihood of diabatic
cooling--and no clear erosion mechanism, one wonders if the wedge
could hang on especially in the areas just below the Escarpment where
it usually takes the longest to erode. Although a general warming
trend will continue, bust potential exists if/where the wedge holds
strong. Assuming the wedge does dissipate or erode by early next
week, temps will be several degrees above climo across the board.

Several members of the ECMWF ensemble, and a couple each in the
GEFS/GEPS, indicate a weak low developing within the moisture plume
along the boundary of the dry high, either in the central/eastern
Gulf or near the east coast of Florida. Such development could
enhance moisture advection and heavy rain potential, although the
most likely scenario remains that developing precip will be light and
of low impact.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: VFR conditions at most terminals through the
TAF period. Mainly cirrus expected through the evening. However, low
level moisture does move in under a subsidence inversion. This
moisture combined with easterly upslope flow will lead to MVFR
stratocu developing along the Blue Ridge and spreading to KAVL late
tonight into the early morning. Some mountain valley fog is also
possible. Some additional VFR stratocu is possible across the area
during the afternoon with low level moisture moving in under the
subsidence inversion. NE winds, SE at KAVL, continue through the
period with gusts around 20 kts returning during the day outside of
the mountains.

Outlook: Dry high pressure is expected to remain over the region
into the weekend. Expect VFR conditions to prevail with the
exception of patchy early morning fog and low stratus in the
mountain valleys each day. Scattered showers may return by Monday.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...RWH/TW
SHORT TERM...Wimberley
LONG TERM...Wimberley
AVIATION...RWH