357
FXUS62 KGSP 060009
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
809 PM EDT Sun Oct 5 2025

.SYNOPSIS...
High pressure continues to dominate the pattern through Tuesday,
with low rain chances and a slow warming trend.  Moisture steadily
increases ahead of a cold front, which arrives on Wednesday.
High pressure and cooler temperatures return behind the front on
Thursday, then persists into next weekend.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 750 PM EDT Sunday...

Key Messages:

1) Max temps near-normal; min temps above normal

2) Patchy mountain valley fog/low stratus possible late tonight
thru early Monday.

3) Spotty showers across the upper Savannah River Valley and
Lakelands again Monday.

Some tweaks to the sky and wx grids with this update. Generally
bumped up cloud cover with CONSShort, as NBM seems underdone. This
may limit mountain valley fog development more than previous
fcst. Also, given the amount of shower coverage we saw today, and
very similar synoptic setup and moisture tomorrow. Have updated
the PoPs for Monday with the latest CONSAll to get more chance
coverage in the Upstate and NE GA Monday aftn.

Otherwise...Inverted surface ridge will continue to gradually weaken
as anticyclone continues to meander away from the Mid-Atlantic
coast. A zone of enhanced E/SE onshore on the southern/western
periphery of the ridge will support a couple of surges of deeper
moisture across the upper Savannah River Valley and the Lakelands
through the period. The first of these is resulting in spotty,
mostly light showers across this area this afternoon...warranting
20- 40 PoPs. Guidance generally agrees that these showers will
diminish by this evening, with shower chances ramping up again
(to 20-40%) late Mon morning into the afternoon in association
with the next moisture surge. The potential for morning valley
fog/low stratus development will increase toward daybreak Monday,
but lingering stratocu responding to upslope and weak upglide flow
will limit its extent and/or residence time. Elevated moisture
and clouds will result in a regime characterized by above-normal
min temps and near- normal maxes.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 1117 AM EDT Sunday: Somewhat of a transitional period
appears likely on Tuesday, as surface high pressure shifts farther
offshore, dislodging its influence on the Carolinas and cutting
off residual cold-air damming from its synoptic source.  A h85
trough should slide across the Eastern Seaboard in the wake of
retreating high pressure, and although this alone likely won`t
be enough to fully scour out the CAD layer...it should certainly
do a number on it, and combined with what operational guidance
still depicts as aggressive daytime mixing, may spell the end
for our resident wedge.  Despite this, temperatures should run
at least a category above normal on Tuesday, owing largely to
weak low-level WAA developing as winds turn more S/SE (SW, even,
by Tuesday afternoon) in response to the advancing h85 trough axis.

The real action will be brewing well upstream of our region
for most of Tuesday and Tuesday night: a potent trough axis
extending from Ontario all the way to the Ozark Plateau will
spend much of Tuesday deepening, and confluent upper flow ahead
of it will amplify the upper pattern across the Carolinas.
Operational guidance depicts a few subtle shortwaves making
tracks across the NC and VA Appalachians as early as Tuesdsay
afternoon and evening...and some ensembles even support low-end
ridgetop showers on Tuesday...convincingly enough to warrant a
slight-chance PoP across parts of the NC mountains.  But, the
system won`t actually arrive until Wednesday, when operational
models are in good agreement that a cold front will dig out of
the Ohio Valley, crossing the Carolinas during the daylight hours.

For the most part, global ensembles suggest that the front will
arrive early enough in the day to beat much daytime destabilization,
and that the core of stronger upper flow will remain displaced
to our north, more toward the VA Piedmont and Chesapeake regions
than in our area...and this scenario would essentially preclude
any chance of significant convective response, keeping us limited
to just some showers along the front.  However, a cluster of
about one quarter of LREF members - mostly comprised of GEFS and
Canadian ensemble members - depicts a slightly less-progressive
upper pattern, and accordingly, a slower FROPA.  This scenario
would give the Carolinas, especially the southeastern half of the
forecast area, longer to destabilize; it`d also bring amplified
upper flow farther south, resulting in at least some opportunity
for thunder, and perhaps weak organization.  None of the CAMs
extend out this far yet, but both the RDPS and regional NAM do,
and both favor the latter scenario.  Watching the hi-res guidance
come in for Wednesday over the next day or so will be interesting.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 1226 PM EDT Sunday: In the wake of the front, a slug of
low-level CAA will stir up N/NW winds for Thursday.  The h85
trough will be deamplifying by this point, so breezier conditions
won`t last much longer than Thursday afternoon.  The supporting
high will wind up parked over New England beneath low-amplitude
shortwave ridging on Friday, but will remain progressive and
is likely, based on the bulk of LREF members, to shift offshore
over the weekend.  As a result, hybrid CAD will redevelop east of
the Appalachians on Friday and Saturday on the north side of the
remnant frontal boundary...which by this point should be somewhere
near the Atlantic coast.  Some guidance depicts a weak open wave
developing along this boundary on Friday or Saturday in response to
shortwave energy originating on the Gulf coast...but this feature
isn`t yet handled very consistently by the long-range ensembles,
and even if such a wave does develop, it`s unclear whether any
associated rain would make it this far inland.  At any rate, it
doesn`t appear to be a particularly significant event apart from
being our next chance for a wetting rain.  It still looks like
temperatures will run quite a bit below normal through the period,
with highs in the 60s on Thursday and Friday, and slowly climbing
back into the 70s over the weekend.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: MVFR to VFR stratocu deck is persisting
across the western half of the forecast area at time of 00z TAF
issuance. Guidance still suggests this cloud deck should thin out
this evening into the overnight, with may allow for some lower
stratus and/or fog to form, mainly in the mountain valleys and
perhaps over the lakes near KHKY. The model guidance has generally
not been bullish enough on these clouds, so confidence in this
scenario playing out is below average. Whatever breaks in the clouds
do form, another round of deeper moisture will work in from the SE
Monday morning, likely producing a few hours of MVFR cigs across the
Upstate and most of the NC mountains. Scattered showers may form
again across the western part of the area, with enough confidence
to warrant a PROB30 for the Upstate TAF sites Monday aftn. KCLT
looks to stay VFR thru the period, but cannot rule out some low
MVFR clouds approaching from the south after daybreak Monday; thus,
will keep sct015 after 12z. Some improvement in the cigs is expected
in the aftn. Winds will be light ENE to NE, except SE at KAVL.

Outlook: Other than the continued likelihood of early morning
mountain valley fog/low stratus, generally VFR conditions are
expected through early week. Chances for showers and possibly
restrictions increase toward mid-week ahead of an approaching cold
front, with cooler and much drier air returning at week`s end.

&&

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

&&

$$

SYNOPSIS...MPR
NEAR TERM...ARK/JDL
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...ARK