207
FXUS62 KGSP 282311
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
711 PM EDT Thu Aug 28 2025

.SYNOPSIS...
High pressure remains in control through Friday then a weak cold
front reaches our area from the north by Saturday. This front
becomes stationary to the south of our region into early next week
with isolated to scattered mainly afternoon and early evening
mountain showers and storms.  Temperatures remain just below
seasonal normals through the first half of next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 710 PM EDT Thursday: Enough moisture and forcing will move in
with the short wave moving in from the northwest for an isolated
shower or two this evening, mainly across the northern mountains and
I-40 corridor. Stratocu and cirrus will diminish overnight as the
short wave moves out of the area. This will bring a better chance of
mountain valley fog overnight. Lows look on track.

Otherwise, the upper trough across the eastern CONUS begins to dig
as an upper low strengthens over Canada. As a result, a shortwave
crosses the southeast tonight. However, the surface high pressure
remains in place and shunts any available moisture out of the area.
Despite the moderate DPVA, there is no QPF response, keeping PoPs
through the near term unmentionable (<14%). That said, an isolated
shower can`t be ruled out this evening. Given all this, confidence
is high for a dry forecast Friday. By tomorrow, the trough starts to
lift northward, resulting in much broader flow across the southeast.
There are pockets of shortwaves that quickly move through the CWA,
but again, moisture remains adrift. Guidance struggles to get the 1
inch PWAT line into the southern counties by the end of the forecast
period. So, again, expecting a dry forecast. Other than a few mid to
upper level clouds during the afternoons, nothing of significance is
forecasted. As the center of the surface high pushes out of the
area, winds become calm to VRB tonight. Similar story for tomorrow.
Lows tonight 5 to 10 degrees below normal. Temperatures east of the
mountains top out in the low to mid 80s with Friday being the
warmest day since the cooldown.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 1215 PM Thu: Height falls still look to occur Friday night as
next vort lobe rotates into the eastern CONUS trough. Overnight into
Saturday morning, PoPs return to the forecast mainly for the
possibility of a weak low moving along the stalled front north of the
Gulf Coast near the base of the trough. Such a development could
induce some degree of warm upglide over the CWA, potentially
resulting in light precip or even an elevated t-storm. Mentionable
chance mainly in the southern half of the area thru Sat morning.
Partly via the height falls, lapse rates will be marginally favorable
thru a deeper layer, so some deep diurnal convection is plausible.
Weak easterly flow associated with sfc high over the eastern Great
Lakes should provide slight mechanical lift leading to an uptick in
PoPs along the east-facing Escarpment. A chance also continues nearer
the frontal zone, in NE GA and portions of the Upstate. PWATs nor
DCAPE appear favorable for either torrential rainfall or notable
downburst potential, and PoPs remain no better than the chance range
as it is, with model support for precip having fallen a bit. Less
cloud cover and potential for diabatic cooling than before, so temps
have also trended slightly warmer Sat, topping out at or a little
below normal.

Cyclonic flow will persist overhead as trough is reinforced by
another vort lobe.  Surface high will push east to the NE CONUS by
late Sunday which should drive a backdoor cold front south into the
CWA that day. As we have seen over the past couple of days, there
remains some spread among models as to how deep the weak low to our
south gets and how quickly it moves toward the Atlantic, although
that spread has diminished. Based on the pattern of QPF response it
appears models key more on the backdoor front. Any way you slice it,
a relatively moist easterly flow will continue Sunday, allowing
continued mechanical lift and/or weak upglide. Temps trend slightly
downward, but PoPs tick upward from Saturday. Chances are highest
along the Escarpment, but at a mentionable value in all zones.
Potential for thunder and heavy rainfall increase more appreciably
compared to the previous day, with moisture return ahead of the
backdoor front increasing PWAT and lowering LCLs, and thereby
boosting SBCAPE. Models vary as to whether the front arrives soon
enough to have a stabilizing effect before peak heating Sunday, so
confidence remains low, but the chance for impactful t-storms Sunday
looks a little greater than it once had.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 120 PM Thu: Backdoor front associated with NE CONUS sfc high
looks likely to have settled thru most or all of the Piedmont by
Monday (Labor Day) morning, with eastern trough regime still in
place.  Easterly flow into the Blue Ridge Escarpment and abundant low
level moisture continue to be a factor for PoPs, maintaining mostly a
high chance value across the mountains and foothills, although
chances trend lower for the I-77 corridor and most areas SE of I-85.
Temps and dewpoints will return to more fall-like values, maxes being
4-7 degrees below normal. Rain chances trend still lower Tue but
temps similar, with the high remaining dominant. The upper trough
will be reinforced circa Wednesday as another open wave swings into
the lower OH Valley; an upper low also is shown to move out of the
Canadian prairie and into the vicinity of Lake Superior. How soon
those features merge is not yet well agreed upon, but of note the GFS
brings in a sfc low with the leading shortwave and thus suggests
widespread precip in our area by late Wednesday, compared to the
largely dry 28/00z ECMWF and 28/12z GDPS. PoPs remain similar to
Tuesday`s for now, with temps slightly warmer but still below normal.

&&

.AVIATION /23Z THURSDAY THROUGH TUESDAY/...
At KCLT and elsewhere: VFR conditions expected through the TAF
period as high pressure remains parked over the area. Mainly cirrus
expected through the period with some VFR stratocu this evening and
again tomorrow afternoon. The one exception could be KAVL where
mountain valley fog is possible. Chance may even be better overnight
than previous few days as skies are expected to clear. However,
confidence too low for TAF mention. S to SW wind continues through
the evening, becoming calm to light and variable overnight. Light
winds pick up from the SW during the afternoon, NW at KAVL.

Outlook: Showers and thunderstorms may return for the weekend into
Tuesday. Fog and/or low stratus may develop each night, mainly in
the mountain valleys.

&&

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

&&

$$

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