357
FXUS62 KGSP 091045
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
645 AM EDT Sun Aug 9 2026

.WHAT HAS CHANGED...
Updated the aviation discussion for the 12Z TAFs.

&&

.KEY MESSAGES...
1. Showers and thunderstorms are expected across the area
mainly this afternoon and evening, with highest coverage in the
mountains. Some of the thunderstorms could become severe today
with damaging wind gusts the main threat, and a few storms could
pose a threat of isolated flash flooding.
2. Temperatures will climb back above normal today, after
which it will be hot and humid each day through Friday. Some
Piedmont/Upstate locations could have afternoon heat index between
98-103 beginning Monday.

&&

.DISCUSSION...
Key message 1: Showers and thunderstorms are expected across the
area mainly this afternoon and evening, with highest coverage in
the mountains. Some of the thunderstorms could become severe today
with damaging wind gusts the main threat, and a few storms could
pose a threat of isolated flash flooding.

As what remains of the weak upper trof to our west lifts out and
fills today, the coverage of showers and storms should be greater
than the past few days. The CAMs certainly agree. An uptick in the
sfc-based CAPE above 3000 J/kg during peak heating will provide
more fuel while we retain enough shear of 15-20 kt to perhaps
provide some organization along cold pools. The environment for
severe weather might appear modest, but there should be enough
dCAPE and sfc-delta thetaE to allow for some strong downdrafts
and a few wet microbursts, thus the Marginal Risk. The heavy rain
potential looks similar to the past few days with fairly high
precipitable water and the potential for back-building storms
like we saw yesterday afternoon, so a few areas could see some
isolated flash flooding. The storms should be highly diurnal. Monday
might be another repeat though the HRRR is not impressed with the
coverage. After Monday, the coverage of storms goes down because
of the developing WNW flow aloft as the mid/upper ridge axis over
the Southeast gets suppressed farther south and a broad upper trof
deepens a bit over the Great Lakes/Northeast. Thus, precip chances
are limited to the NC mountains Tuesday thru Thursday. There is
some indication in the guidance that we could end up in an MCS
track by mid-week if the eastern upper ridge gets much deeper, in
which case our precip probs are deficient for the second half of the
week. That is a very low confidence scenario at this point, however.


Key message 2: Temperatures will climb back above normal today,
after which it will be hot and humid each day through Friday. Some
Piedmont/Upstate locations could have afternoon heat index between
98-103 beginning Monday.

Today should be the subtle transition day as the upper trof to our
west finally breaks down and fills, while the Atlantic Subtropical
Ridge builds westward over the Deep South. The latest guidance has
raised temps a few degrees for today, and as a result we go above
normal on highs beginning today instead of Monday. Fortunately,
the dewpoints don`t respond sufficiently to raise the heat index
today, so it should be merely hot but not dangerously hot. The
warming trend through the middle part of the week will also be
accompanied by gradual increase in dewpoint as well, which should
push the afternoon heat index up to the 98-103 degree range over
a good bit of the western Piedmont/Upstate/Lakelands areas each
afternoon. Confidence in reaching Heat Advisory criteria remains
relatively low because the overall pattern looks unsupportive of
really hot temps. By Tuesday, the WNW flow aloft should contribute
some downslope warming, but also suggests some potential to mix out
the dewpoint in the afternoon, which would offset the warming. Also,
the guidance suggests a greater potential to be in an MCS track
from Tuesday onward, so debris cloudiness and organized convection
could also prevent the really high heat index any day. Once we
get to the late part of the week, the western ridge is expected to
migrate eastward and undergo some amplification, which would bring a
boundary down from the north and cool us off a bit for next weekend.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: KAVL and KHKY are the problem spots this
morning. At KAVL, the valley has filled with low stratus as shown
by satellite imagery. The cloud base was at the LIFR level, which
should persist through mid-morning until it scatters. Visibility
will be variable between VFR and LIFR. At KHKY, fog near the
river will make flight conditions highly variable between VLIFR
and VFR through 13Z-14Z. Other terminals are expected to stay VFR
with light/variable wind. Today looks more convectively active by
early afternoon. We could pop a brief MVFR ceiling this morning
as cu forms, but then scattered to numerous showers and storms
will form. Confidence is high enough at KAVL to go with a TEMPO
starting in early afternoon, but the other terminals will be
held at PROB30 for now. A strong diurnal tendency is indicated,
so the convection should be done shortly after sunset. Thereafter,
just convective debris. Wind should be light SW. More fog can be
expected early Monday where it rains today/tonight.

Outlook: Scattered showers and thunderstorms, with associated
flight restrictions through early next week. Patchy fog and low
stratus is possible each morning, especially in the mtn valleys
and anywhere that received significant rainfall.

&&

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

&&

$$

PM