156
FXUS62 KGSP 061857
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
257 PM EDT Sun Sep 6 2026

.WHAT HAS CHANGED...
Severe Thunderstorm Watch in effect for Upstate SC and some
adjoining counties of GA and NC until 9 PM EDT.

&&

.KEY MESSAGES...
1. Clusters of thunderstorms will move through the area this
afternoon and evening, some of which may produce damaging winds and
large hail, in addition to torrential rainfall possibly causing
isolated flash flooding. Scattered heavy downpours may redevelop
in some locations in the late evening or overnight and also could
cause isolated flash flooding. Make sure you have multiple ways
to receive warnings, especially if you have outdoor plans.
2. Rain chances linger Monday before drier conditions return
Monday night, persisting through mid-week. A cold front will
bring rain chances back towards the end of the week.

&&

.DISCUSSION...
Key message 1: Clusters of thunderstorms will move through the area
this afternoon and evening, some of which may produce damaging winds
and large hail, in addition to torrential rainfall possibly causing
isolated flash flooding. Scattered heavy downpours may redevelop
in some locations in the late evening or overnight and also could
cause isolated flash flooding. Make sure you have multiple ways
to receive warnings, especially if you have outdoor plans.

A northwest flow pattern will continue in the upper levels across
the Carolinas and northeast Georgia through Monday, driven
by a deep ridge over the central CONUS and a deep trough over
the Great Lakes and Eastern Seaboard, surrounding a closed low
near the Canadian Maritimes. At the surface a somewhat diffuse,
almost stationary front persists from western KY to the NC/VA
Tidewater region. The front will make slow southward progress
through Monday. Vort lobes rotating through the trough, combined
with low-level convergence in the frontal zone, once again will
enhance development of convection. Modest effective shear of
25-30 kt will promote organization of storms. Shear vectors
are expected to remain somewhat parallel to the frontal zone
and slow-moving linear clusters appear possible. 2500-3000 J/kg
of SBCAPE is in play south of the front and at least marginally
severe (quarter to ping-pong ball size) hail cannot be ruled out,
though the greater threat would appear to be wind; DCAPE should
be sufficient for individual storms or clusters to pose a risk of
damaging winds. SPC Day 1 Convective Outlook remains in Slight Risk
(level 2 of 5) for most of the CWA, and a Severe Thunderstorm Watch
has been issued for a portion of our southern CWA, valid til 9 PM.

Instability will wane nocturnally this evening, though lapse rates
remain favorable for some degree of elevated convection. As the
front sags farther south and high pressure builds from the Great
Lakes into the mid-Atlantic, low-level flow turns more easterly;
overall slow storm motion will continue, but flow aloft remains
westerly and this suggests remaining convection may "anchor"
along east-facing terrain. PWATs will trend downward slowly from
north to south following the advance of the high pressure, though
not fast enough to preclude a threat of isolated flash flooding,
particularly due to the anchoring or where the overnight precip
amounts to a second round of heavy rain, following storms this
afternoon. WPC also features a Slight Risk for an area east of
the Blue Ridge Escarpment and nearest the overnight position of
the front as a result.


Key message 2: Rain chances linger Monday before drier conditions
return Monday night, persisting through mid-week. A cold front
will bring rain chances back towards the end of the week.

Easterly low-level flow continues Monday as the front settles to
our south and we come under the influence of a somewhat wedge-like
surface high nosing south into the region. Areas of fog and
low stratus may linger well into the morning though clouds are
expected to scatter over much of the Piedmont for the afternoon. A
few showers may linger though with lower PWATs and far less
instability, the threat of heavy rain is much lower. Temperatures
will trend 10-15 degrees cooler, with maxes in the mid-70s to lower
80s. We remain fairly humid through this period. PoPs fall to 10%
or less for most of the area Monday night and remain low through
Wednesday night. Temperatures do moderate as heights rise aloft
and the sfc high sets up offshore, nearly back to normal Tuesday
and then slightly above normal Wednesday.

Subtle upper height falls do begin over the Appalachians again
Wednesday night as a mature cyclone moves across central Canada,
pulling the next front into the mid-MS and OH valleys. Slight
return flow develops in advance of that feature, warranting chance
PoPs returning for the mountains on Thursday. Some of the global
models, especially the Canadian GDPS, show the surrounding broad
trough inducing a wave along the stalled front, generally near
south Georgia, with small PoPs also being warranted for the lower
Piedmont on Thursday as a nod to that possibility. 40-60% PoPs
expand to the whole area Friday near the Ohio Valley cold front. The
orientation of the front is not especially conducive to a strongly
forced severe weather event, and destabilization appears limited
ahead of it. Quasi-zonal upper flow persists into next weekend
so the front could stall near the region and maintain unsettled
weather. Seasonably warm and muggy conditions should continue.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Clusters of TSRA are on track to affect
KGSP/KGMU through mid-afternoon with some chance for all the other
terminals. TEMPO for generally IFR vsby and VRB gusty winds in
turn. A cold front will slowly sag southward through the region
this evening and conditions will be favorable for some SHRA or
isolated TSRA to linger into the night. Most likely this activity
will end by 06z, and PROB30 was included mainly with only SHRA
mentioned. Easterly flow developing behind the front suggests
areas of MVFR to IFR stratus will develop late in the night and
linger through daybreak. Some areas of fog also may develop though
with breezy NE winds think cigs will be the main concern. Slow
improvement back to VFR expected late morning to midday.

Outlook: Drier conditions return by Monday night, lingering
through mid-week.  This should allow VFR to return outside of
morning mountain valley fog and low stratus.

&&

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

&&

$$

JCW