121
FXUS62 KGSP 011738
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
138 PM EDT Mon Sep 1 2025

.SYNOPSIS...
High pressure will remain over the East Coast through Tuesday,
then gradually weaken midweek. It will be mostly dry, until
greater coverage of the showers and storms returns across mostly
the mountains and adjacent foothills into Wednesday and Thursday as
a weak cold front approaches from the northwest. Temperatures remain
below seasonal normals through Thursday.  An upper ridge may build
eastward from Texas over the weekend resulting in a warming trend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 120 PM EDT Monday: Inverted surface ridge axis supporting
relatively cool and dry conditions...making this feel more like
October 1st than September 1st...is forecast to begin a steady
weakening phase tonight into tomorrow, as confluent flow weakens
atop the East in response to upper low...currently centered over
the Mid-Atlantic retrograding to the eastern Great Lakes and forcing
the long wave trough to become re-established to our west. As such,
humidity and temperatures will increase slightly for Tuesday,
while still remaining below climo.

In the interim, moisture lingers and weak instability has
developed in areas displaced from the ridge axis...i.e., the
TN border counties mainly SW of I-26 into extreme northeast
GA...where a decent amount of congestus is developing along the
ridge tops. Expect isolated convection to develop in these areas
shortly...mainly showers, but isolated TS are also expected. Updraft
intensity/rainfall rates will be limited by the meager instability,
but some locally heavy rainfall is possible with any cells that
become anchored along terrain features. Any convection is expected
to dissipate by mid-evening. For Tuesday, adequate moisture and
weak instability is forecast to again be confined to approximately
this same area, and PoPs of 20-30% will again be generally confined
to those locations.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 123 PM EDT Monday: The guidance continues to indicate a mean
long wave mid/upper trof over the East for Wednesday into Thursday
as an old upper low lifts over eastern Canada and gets absorbed by
the next large upper low dropping down over the upper Great Lakes
and western Ontario. This next sprawling system will keep the trof
axis to our west through Thursday and the best precip chances
off to the west, at least on Wednesday. The main player will be
a fairly potent-looking short wave dropping down into the trof to
our west. Not a tremendous influx of Gulf moisture ahead of this
wave, but the trend in the guidance is away from any weak system
off the Southeast Coast which would afford a better opportunity to
entrain more moisture from the south. This could come more into
play on Thursday depending on how quick the wave is. Some of the
guidance has the short wave moving east late Thursday, pushing this
initial sfc boundary across the region late in the day and offering
some focus for thunderstorms. As alluded to previously, some of
the medium range severe weather guidance is latching onto some
potential for strong storms Thursday/Thursday evening, though that
potential might be best on the west side of the mtns. The boundary
should be driven east across the area by late Thursday night. The
guidance blend keeps the area S/E of I-85 largely precip-free with
the frontal passage, but enough of the guidance is trending toward
greater precip coverage that precip chances will probably go up over
the eastern zones during that period. Temps still look to rebound
further on Wednesday as any lingering CAD-like residue should be
wiped out, then we climb back to normal temps for Thursday as the
boundary approaches from the west.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 1225 PM EDT Monday: At face value, the fcst looks relatively
benign from Friday onward, assuming the primary cold front clears
the eastern zones before daybreak Friday. The model blend continues
to trend warmer on the temps for Friday into Saturday, which
makes sense because the mid/upper trof orientation doesn`t really
change with short wave ridging moving through the trof on Friday
and another short wave trof dropping down and keeping the axis of
the long wave trof to our west through most of Saturday. There
won`t be much of an air mass change as a result, and with warm
advection continuing ahead of a secondary cold front, temps could
easily climb back above normal by 3-5 degrees both days. So, it
looks like one of those autumn situations when temps are actually
warmer behind the alleged cold front. The secondary front could
be a bit interesting if the timing is such that it moves through
late in the day as in the old ECMWF solution, because there would
be the opportunity to grow some thunderstorms with enough shear to
provide some organization. For now, however, we limit the fcst to
a slight chance of precip mainly over the mtns and foothills. Once
the secondary boundary comes through, more of an air mass change
will take place, with temps dropping back down at or slightly
below normal with lower RH as high pressure builds back in from
the northwest for Sunday and Monday.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Unseasonably dry air is expected to
support VFR/mostly SKC conditions at the TAF sites through the
period. Scattered convection is expected this afternoon near the
TN/NC border, but this activity should remain west of KAVL. Can`t
completely discount the potential for low stratus and/or fog at
KAVL around daybreak Tuesday, but this appears unlikely at this
time. Winds will generally favor NE at 5-10 kts this afternoon,
weakening to around 5 kts this evening before increasing slightly
late in the forecast period. Some gusts in the 15-20 kts range
are possible at all sites except KAVL and KHKY this afternoon.

Outlook: At least scattered afternoon/evening convection will
return for much of the area Wed and Thu before diminishing again
late in the week. Nocturnal valley fog and/or low stratus will
also be possible each night and early morning, especially at
mountain terminals.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...JDL
SHORT TERM...PM
LONG TERM...PM
AVIATION...JDL