423
FXUS62 KGSP 041046
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
646 AM EDT Thu Sep 4 2025

.SYNOPSIS...
Scattered showers and a few thunderstorms will be possible this
afternoon ahead of an approaching cold front. The cold front stalls
to the northwest with a warming trend Friday and Saturday. Rain
chances return Saturday into Sunday as the front finally pushes into
the area. Cooler and drier weather returns next week behind the
front.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 140 AM EDT Thursday: An upper-level vort max can be seen
crossing eastern TN thru central GA, and is helping trigger
convection across the Great TN Valley. This activity is
approaching the Smokies, where models show only a few hundred
J/kg of CAPE and some CIN. So the tstms should weaken, with just a
few showers expected to make it into the western NC mountains thru
daybreak. Increasing SWLY flow is producing some stratocu across the
mountains, but so far doesn`t look like enough to completely sock
in the valleys. Thus, still expected fog to form in the mountain
valleys, which could be locally dense. Patchy fog is also forming
in the NC foothills, but the rest of the CWFA should see just
thin cirrus.

The vort max will push east of the area early this morning, but
more spokes of vorticity will continue to rotate thru a large,
broad eastern CONUS upper trough. The strongest forcing still
looks to remain north of the forecast area, with weak to neutral
synoptic forcing to speak of today. But with the deep trough in
place, bulk shear will be around 30-40 kt. Decent instability will
materialize upstream across central/eastern KY/TN. Convection
should fire along/ahead of a cold front that is sagging SEWD
thru the OH Valley. Pre-frontal convection is also likely to
form in the mountains. Overall, CAPE is expected to stay below
2000 J/kg. And with the lack of good forcing, convection will
struggle to organize. With that said, a line of storms may get
going over the Cumberland Plateau by late aftn, and approach the
TN/NC border by 00z. The 00z CAMs are not that excited about this,
showing fairly disorganized convection. The new Day 1 SPC convective
outlook is little changed from yesterday`s Day 2 outlook, keeping
the marginal risk across our mountains and foothills. The main
threat will be isolated damaging wind gusts. As for the rest of
the forecast area, little CAPE to work with, along with lack of
low-level convergence suggests little convection will survive
east of the mountains beyond the adjacent foothills. It will be
marginally breezy, with winds picking up out of the SW, gusts up to
20 mph possible. Highs will warm to near normal across the Piedmont,
but remain a category or so below normal in the mountains.

Tonight, the cold front stalls out to our NW, while convection
wanes. There may be some lingering cloudiness, but overall, skies
will clear and allow for mountain valley fog to develop during
the pre-dawn hours. Patchy fog cannot be ruled out elsewhere, as
dewpts remain elevated. Lows will be mainly in the low to mid 60s,
which is a few degrees above normal.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 1141 PM Wednesday: A vertically stacked closed upper low will
continue to meander across eastern Ontario Friday with a broad
trough extending from the Northern Plains to the Ohio Valley.
Heights are forecast to rise across the Southern Appalachians as a
lead shortwave trough lifts across New England while a second trough
dives across the Northern Plains. A surface cold front is expected
to remain stalled across the Ohio Valley as upper forcing wanes and
the front becomes oriented parallel to upper flow within the base of
the mean trough. This will support a warming trend across the
western Carolinas and northeast Georgia with highs climbing into the
upper 80s to low 90s outside of the mountains. By Saturday, the
shortwave diving across the Northern Plains will have swung across
the Great Lakes and is progged to be lifting towards New England
while a third piece of energy drops into the Central Plains. At the
surface, a large sprawling surface high will drop out of the
Canadian Prairies and into the Great Plains and will help to finally
kick the stalled frontal boundary into the area. A round of at least
scattered showers and thunderstorms will be possible across the
area, especially over the mountains, as the front moves through on
Saturday. H5 heights will be rather high with only subtle height
falls and meager severe weather parameters. Thus, while a strong
storm or two cannot be discounted, confidence is low in regards to
the potential for organized severe weather with the frontal passage.
Warm temperatures in the mid 80s to low 90s will continue on
Saturday.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 1153 PM Wednesday: Guidance has come into better agreement as
the weekend comes to a close with most members converging on a
solution that favors the frontal boundary clearing the area and not
stalling. The speed of the boundary still remains somewhat uncertain
with some pieces of guidance still lingering the front over the area
on Sunday. If this scenario is realized a few showers could also
linger into Sunday before the boundary fully clears the area. Drier
and cooler weather returns behind the front next week as the
previously mentioned surface high quickly slides into the Ohio
Valley on Monday before lifting into New England Tuesday and
Wednesday. Eventually, a dry CAD pattern appears likely to take
shape as the high translates across the Appalachians. The surface
high remains rather progressive and shifts offshore by midweek, but
dry air and northeast flow will remain in place across the area.
Afternoon highs are forecast to fall below 80 across most of the
area on Monday with very gradual warming back into the low 80s by
mid to late week. Overnight lows will also be cool in the low to
upper 50s.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
At KCLT: Increasing SW flow ahead of an approaching weak cold
front is producing scattered showers and tstms that are moving
into western NC and extreme NE GA. The activity is more robust
than expected, and may impact KAVL this morning. Some may also
pass by just north of the Upstate TAF sites. The increasing
flow will allow for a little more wind out of the SW, with some
gusts in the 15-20 kt range possible across the Piedmont in the
aftn. Another round of scattered convection is expected to develop
this afternoon, with some of that activity tracking into the
adjacent foothills. Confidence is barely high enough for a PROB30
at KGMU/KGSP, with better chances at KAVL and KHKY. Chances are
still too low for any mention at KCLT, with most of the convection
staying north and west. Convection should diminish this evening,
leaving some lingering VFR clouds into the overnight. Mountain
valley fog will be likely late tonight thru daybreak Friday.

Outlook: Drier conditions return Friday. Another cold front will
bring a chance of showers and thunderstorms on Saturday, mainly in
the mountains. Then lingering chances of mainly showers on Sunday
across the Piedmont. Dry weather returns Monday. Nocturnal fog
and/or low stratus will be possible each morning, especially in
the favored mtn valleys.

&&

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

&&

$$

SYNOPSIS...TW
NEAR TERM...ARK
SHORT TERM...TW
LONG TERM...TW
AVIATION...ARK