436
FXUS62 KGSP 042354
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
754 PM EDT Sat Oct 4 2025

.SYNOPSIS...
High pressure continues to dominate the forecast the next few days
as temperatures warm up slowly.  Moisture returns early next week,
allowing cloud cover and rain chances to increase ahead of a cold
front, which should arrive on Wednesday.  High pressure and cooler
temperatures return toward the end of the period.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 730 PM EDT Saturday...

Key Messages:

1) Temperatures a Little Above Normal

2) Mountain Valley Fog/Low Stratus Possible Again Sunday Morning

3) Small Shower Chances for the Upper Savannah Valley/Lakelands

SELY upglide flow will likely persist thru the night, producing
varying amounts of stratocu across much of the SC/GA zones, and into
the southern and central NC mountains. The clouds are expected to be
too shallow to produce any precip, but they may limit fog potential
somewhat in the usual mountain valleys. Sky cover bumped up with
the aviation forecast update. Otherwise, the forecast looks good.

Deep anticyclone will continue to meander off the Carolina/Mid-
Atlantic coast through the near term, resulting in continued/gradual
weakening of the inverted surface ridge in place across region. Flow
just above the surface turning to the SE around the periphery of the
weakening ridge is expected to result in advection of an Atlantic
moisture plume into mainly the southern/western part of the CWA by
late Sunday morning, resulting in increasing shower chances...albeit
only in the 20-30% range across the Lakelands region/upper Savannah
River Valley by afternoon. Otherwise, another round of fog/low
stratus is expected...mainly in the mountain valleys, but it
may be a little less widespread than Saturday morning owing to
lingering cirrus as well as the increased potential stratocu to
develop prior to fog formation. Min temps tonight are expected
to be warmer than in recent days...very close to normal. Maxes
on Sunday should be similar today...perhaps even a degree or two
cooler owing to increased cloud cover potential.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 1214 PM EDT Saturday: The upper anticyclone centered over the
Eastern Seaboard will become increasingly lopsided Monday as a broad
area of confluent flow develops over the central CONUS.
In response, surface high pressure will drift farther and farther
offshore, steadily reducing synoptic support for the lingering
cold-air damming in place east of the Appalachians.  As a result,
the wedge will wind up orphaned and should slowly deteriorate
through the remainder of the short term.  Still not carrying a PoP
on Monday, but the latest operational GFS and ECMWF both depict a
lobe of stronger low-level isentropic ascent developing along an
axis from central Georgia into the CSRA and western SC Upstate
on Monday evening.  There`s some discrepancy among ensembles
over exactly how far north this upglide will find its focus,
which will determine how it affects us...but still think the
potential for isolated sprinkles late Monday is there.  Highs on
Monday will largely be dictated by thicknesses...as although the
upper anticyclone will begin to slide east by peak heating Monday,
thicknesses will remain anomalously high, and resulting temperatures
should wind up a solid category above normal for most of the area.

Tuesday, what`s left of the z500 high will retreat farther south and
east, eventually merging with the subtropical ridge over the Gulf
and western Atlantic.  Heights over most of the Eastern Seaboard
will fall as robust troughing intensifies over the Great Lakes and
southeastern Canada, while an elongated cold front slips into the
Ohio Valley.  By Tuesday afternoon, weak near-surface WAA should
support development of a decent mixed layer, scouring out clouds
across much of the low terrain...and especially areas south of I-85.
Highs will once again climb at a category or more above normal.
By the end of the period Tuesday evening, the front will likely
be entering the Tennessee Valley, though associated precipitation
doesn`t look like it`ll make it to the Carolinas until well after
nightfall.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 1231 PM EDT Saturday: Wednesday still looks to feature the
next opportunity for active weather...though using the phrase
"active" may be a bit of an overstatement.  The general consensus
is that the most-focused region of the advancing upper trough axis
will remain well north of the area, which in turn should keep the
better synoptic forcing somewhere over the Mid-Atlantic.  For us,
the lack of either DPVA or significant height falls means lapse
rates won`t improve much ahead of the front, and the incipient
dry air mass will make surface-based instability...difficult to
come by.  Most operational guidance depicts <1000 J/kg sbCAPE
developing ahead of the front Wednesday, and the global ensemble
consensus is much lower.  Should appreciable instability develop,
there`s an opportunity for some overlap with better deep layer
shear along the northern tier of the CWA - there`s a whole group of
LREF membership that favors a slower-moving, more-compact trough
axis across Virginia and the northern portions of North Carolina
- and this could result in at least loosely-organized showers
and a few thunderstorms across the NC Foothills and Piedmont.
All that said, the potential for severe weather remains quite low;
it`s more likely that we`ll just get a wetting rain, maybe some
thunder, and then move on.

Guidance remains in good agreement that the front will sag as far
southeast as the Atlantic coast on Thursday, while a postfrontal
surface high migrates out of Alberta and becomes parked over
New England for the remainder of the period.  Surface maps are
reminiscent of hybrid CAD, though they depict a less prominent
surface ridge than the one earlier in the week, and generally
favor more of a NNE low-level flow than an E low-level flow...which
seems to confirm the idea that a develop CAD might be weaker and
have a harder time getting a foothold.  Regardless, postfrontal
temps should cool considerably...with highs on Thursday, Friday,
and Saturday only in the low- to mid-70s.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Not much change in the forecast for the
00z TAFs. A mix of stratocu and cirrus will continue across the
area tonight thru Sunday. These clouds make the confidence on
fog development low. The clouds are not expected to develop into
a persistent overcast, and even just a few breaks here and there
may allow mountain valley fog to form. Also, cool overnight temps
will likely result in some lake fog, which may impact KHKY again
early Sunday morning. After daybreak Sunday, some of the lower
stratocu may drop below 3000 ft in spots thru about 16z, mainly
in NE GA and the western Upstate. Guidance is not in agreement
on this, so confidence remains low on this as well.  Otherwise,
VFR conditions are expected thru the period. Isolated to scattered
showers may develop in the aftn, mainly west of the TAF sites,
with KAND having the highest chance (10-20%) of seeing showers
around. Coverage still looks too low to mention in any of the 00z
TAFs. Winds will be light/variable or E/NE overnight, then pick up
slightly out of the E/NE 5-10 kt in the morning (except SE at KAVL).

Outlook: Other than the continued likelihood of early morning
mountain valley fog/low stratus, generally VFR conditions are
expected through at least early next week. Chances for showers
and possibly restrictions increase toward mid-week ahead of an
approaching cold front.

&&

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

&&

$$

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