Stamey Branch, North Carolina Weather Forecast Discussion

462
FXUS62 KGSP 251104
AFDGSP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
704 AM EDT Thu Sep 25 2025
.SYNOPSIS...
An unsettled pattern emerges ahead of a cold front and upper
trough with multiple rounds of showers and thunderstorms into the
weekend. Temperatures remain warm through today before cooling to
near seasonable normal high temperatures into early next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 1245 AM Thu: Warm advective regime will continue over the CWA
today ahead of well defined trough axis moving thru the mid MS and
lower OH valleys. Area of precip will track across the CWA early
this morning as a remnant of an earlier linear MCS in TN/GA. This
activity should continue to decay although it has outpaced all
the guidance, so hourly PoP trends are based on extrapolating
the observed storm motion. It now appears most of the upper
divergence which had previously been shown over the mountains
early this morning was simply a result of upstream convection,
so with that now having passed much of the mountains, PoPs are
lower thru daybreak, although some vort blobs are still analyzed
upstream by the RAP and upslope flow could allow showers to respawn.
Not terribly impressed with the synoptic support for convection
today. The positive tilt of the trough is not favorable for
coherent DPVA into the area, and what vort is shown on models
entering our area appears to generate from convective bands in
AL/GA. The right-rear quad of a 250mb jet streak is in position to
offer some upper divergence; SW`ly 850-700mb flow should allow some
isentropic lift although that too is not particularly strong, and
appears likely to keep midlevel cloud cover over much of the area,
limiting destabilization. Not terribly confident in CAM output
given the poor handling of this morning`s convection and potential
for area to remain somewhat worked over, but they variously depict
scattered initiation over the mountains this afternoon, and largely
develop loosely organized activity exiting GA as noted above. 0-6km
shear is modest at 25-35 kt, increasing a bit further late in the
day, so it is to be expected activity may organize. Severe threat
most likely would be from damaging winds although marginally severe
hail can`t be entirely ruled out, if we manage enough instability;
CAPE profiles are fairly skinny on account of the deep moisture
expected. The western two-thirds of the CWA get a likely to
categorical PoP in the early to mid afternoon but values peak at
chance farther east, furthest from the dynamic lift. As previous
shift noted, differential heating along the edge of the cloud deck
may play a role in initiation, both in south AL/GA and in our CWA,
the most likely place being in our lower Piedmont.
Tonight, the progress of the trough toward our area slows as low
begins to cut off over KY/TN. Elevated CAPE remains muted with
isentropic lift weakening as midlevel winds veer to westerly. Most
areas receive only chance PoP with CAM response largely turning
to isolated to scattered showers by mid-evening. Widespread low
cloud cover looks to develop and likely areas of fog.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY/...
As of 125 AM EDT Thursday: There still appears to be a cold front
approaching the area and that should still bring in cooler
temperatures by Friday night. Meanwhile, a split trough develops an
upper low well west of the area and remains the dominant feature
through the weekend. As the frontal boundary stalls and struggles to
make it through the CWA, the area of low pressure increases WAA from
the south and feeding into more shower and thunderstorm activity
through Saturday night. By the end of the period, the low begins to
retrograde more NE, eventually centering over the Carolinas. Model
guidance puts the better DPVA and forcing from this low over the
area Friday night, enhancing rain chances. At this time, the better
QPF response has shifted eastward. This could change as model
guidance through these last few forecast cycles have not been the
greatest. But for now, it looks like the main QPF is more in the
eastern portion of the CWA and not in the mountains. The range of
rainfall totals are 0.3-1.5 inches over the entire short term, with
the heavier amounts looking to be in the eastern NC Piedmont. Model
soundings for Friday and Saturday shows instability of 500-1000 J/kg
of sbCAPE during the afternoon/evening timeframes, supporting
convection. Though broad severe weather is not expected, cannot rule
out a few strong thunderstorms daveloping during these days. This
will also enhance precip rates, so a few isolated nuisance flooding
issues are possible. For now PoPs havent changed much for Friday and
Saturday (50-80%). As for the temperatures, the frontal passage
finally brings the daily highs into the normal range with Saturday
being a bit cooler.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 130 AM EDT Thursday: By Saturday night and onward, the model
guidance continues to be unclear and funky for the general pattern.
Aloft, the GFS/EURO wants to cutoff the low pressure over the TN
Valley and have it churn over the area into Monday. Meanwhile, the
general flow across the CONUS appears to have a strong upper ridge
forming as high pressure works its way through the central and into
the eastern parts of the country. Additionally, the long range
guidance still cannot figure out how these storms in the Atlantic
will play out and IF there will be any impacts for the Carolinas.
Still monitoring, but at this time, there is nothing anticipated.
After Monday, the forecast is even more uncertain. Still appears to
be unsettled with a few showers possible each day, but confidence is
very low at this time. Will keep PoPs at slight chance (15-25%)
after Monday. Temperatures are expected to remain more seasonable
and normal.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: LIFR cigs popping in and out at KAVL and
KHKY likely due to river valley effects and with rain having fallen
overnight. Another area of RA is reentering the NC mountains and
GA/SC foothills seemingly with low level upglide and/or mechanical
lift into the terrain. Some areas of MVFR cigs appear likely to
develop during or after the precip. Prevailing SHRA at KAVL but
with less confidence it will reach KHKY only VCSH. Plentiful high
altitude cloud cover will linger over the area this morning and puts
diurnal instability somewhat in question, which has implications for
diurnal SHRA/TSRA development this afternoon ahead of approaching
cold front. While the surface front itself probably will remain
west of the area tonight, dynamic lift will increase and enough
instability is expected to persist for scattered convection
during the evening. TEMPO or PROB30 generally used for afternoon
convection, with the opposite used except where chance remains
elevated in the evening. Generous use of VCSH given persistent
low chance throughout the day and evening. Widespread restrictions
likely to develop tonight as convection wanes and with plentiful
moisture and weak near-sfc lift. Winds generally favoring SW`ly when
not VRB, although KAVL could flip to NW tonight if not going calm.
Outlook: Shower and thunderstorm chances, as well as associated
restrictions, continue for all terminals into the weekend thanks to
a cold front. Mountain valley fog and low stratus are possible each
morning but could be limited somewhat by both cloud cover and rain.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...CP
NEAR TERM...Wimberley
SHORT TERM...CP
LONG TERM...CP
AVIATION...Wimberley

NWS GSP Office Area Forecast Discussion