340
FXUS62 KGSP 190604
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
204 AM EDT Tue Aug 19 2025

.SYNOPSIS...
The chance of afternoon and evening showers and thunderstorms
slowly increases into the weekend. Temperatures start out near
normal then fall below normal for the weekend. Cooler but drier
conditions develop on Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1:45 AM EDT Tuesday: We`re still seeing sct showers and a
few embedded thunderstorms over the Upstate and southern NC mtns
as we head into the overnight. This activity will likely linger
for a few more hrs, but any impacts should be minimal.

The weak sfc front should continue to drift south overnight while
a large sfc high over Quebec noses down east of the mtns in a wedge-
like fashion. Guidance continues to show increasing low-lvl moisture
on a developing ENE flow that gets pushed up against the Blue Ridge
Escarpment. Some of the CAMs redevelop more shower activity on/near
the NC Escarpment thru the early morning hours, possibly moving SW
over the northern Upstate/northeast GA toward daybreak. This poten-
tially poses an outside threat for heavy rain and localized flash
flooding if cells can get anchored near the Escarpment for long
enough. Thus, PoPs are kept thru the overnight over these areas,
but the rest of the fcst area should be mostly dry. Otherwise, low
temps should be seasonally mild. For the rest of today, the situation
is more of a look-alike than a real wedge, with weakening sfc high
pressure over New England and the Canadian Maritimes but with NE flow
lacking enough static stability to lock in cold air damming. Guidance
indicates enough sfc-based CAPE across most of the region to account
for the development of convection in the afternoon. PoPs remain above
climo over the NC mtns, northeast GA, and the western Upstate due to
the enhanced low-lvl convergence, but below slight chance over the NW
Piedmont where drier air advects in from the NE. With the increased
cloud cover, high temps are expected to remain a few degrees below
normal across our area.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 1230 AM Tue: Positively tilted shortwave will be present over
the NE CONUS Wednesday morning, with attendant cold front extending
down the Ohio Valley. Hurricane Erin will churn northward off the
Carolina coast. Weak high pressure will continue to nose into our
CWA from the NE between these features. Slight subsidence either on
the periphery of Erin, or from the high itself, makes vertical
profiles unfavorable for deep convection across the lower Piedmont;
accordingly with minimal QPF response there PoPs remain below slight-
chance during the day. The frontal convergence zone however impinges
on the Appalachians late in the day, and profiles appear less
subsident there, warranting 40-60% PoPs. Skies remain mostly clear
and temps will warm back slightly above normal, near 90 in most of
the Piedmont. The front could keep mountain convection bubbling into
the evening, although CAM simulated activity drops off by 06z Thu.

By early Thursday synoptic models depict Erin`s upper circulation
beginning to merge with the aforementioned shortwave, leading the
storm`s track to recurve toward the open Atlantic. Some DPVA will
occur over the CWA as the trough axis sags into our area; low levels
moisten again and PWATs rise back above normal over the Piedmont,
with subsidence also weaker. PoPs tick higher across the board with
convection more easily developing. Values notably rise back into the
chance range over the SE half of the CWA, and with chances persisting
through Thursday night, the best chance at that time being near and
southeast of I-85. Temperatures remain near normal Thu in the
Piedmont and a little below normal over the mountains.

With the above-normal PWAT developing Thursday, and that plus
elevated instability likely to persist Thursday night, the threat of
locally excessive rainfall will increase. As Erin pulls away, sfc
high pressure develops over the East Coast, driving a backdoor cold
front southwest thru the CWA Thu night. North of the front, E to SE
near-sfc flow solidifies, while upper level flow remains out of the W
to NW.  This could promote anchoring of convection along the
east-facing terrain, but storm motion will otherwise be slow.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 110 AM Tue: The backdoor cold front looks to continue to push
slowly southwestward Friday. Moist upslope flow will continue into
the Blue Ridge; widespread cloud cover is expected and considerably
above-climo PoPs are forecast. Profiles may be slightly less
favorable for deep convection due to weak subsidence, but the
upslope lift offers the possibility of some elevated CAPE being
realized. Likely values are fcst throughout the mountains and in the
Savannah Valley nearer the front.  Temperatures trend 5-8 degrees
cooler and most areas remain near or below 80 but with high
humidity.  There appears little effective change in the pattern for
Saturday, although sfc high will drift off the East Coast, and low-
level flow will veer to a more southerly direction as heights fall
in the Midwest ahead of the next broad shortwave. The change in
direction could move some of the focus for convection to the south-
facing Blue Ridge. Also, a baggy upper trough is progged to form
over the frontal zone and the subsidence inversion is weaker.
Abundant cloud cover and precip should make for a day pretty similar
to Friday, with similar temps and PoPs. Excessive rainfall will
remain a concern with convection likely to be slow-moving and
possibly anchoring, though the likelihood of flooding may be
mitigated by the highest PWATs being south of the mountains, nearer
the front.

By Sunday morning the baggy trough looks to advect east such that the
CWA may be under greater subsidence. Cold front associated with the
Midwest trough should reach the Appalachians late in the day. Cloud
cover looks to thin, PoPs decline owing to the subsidence, and
compressional warming ahead of the front leads to slightly warmer
temperatures, largely 80-85 in the valleys and Piedmont. Cooler and
drier air will spread over the area Sunday night; some higher
elevations will see lows drop to around 50 Mon morning. Max temps
Monday will be similar to Sunday`s, but with considerably lower
dewpoints. Still cooler temperatures look to follow for the middle of
next week.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: We`re still seeing sct showers and a
few embedded thunderstorms over the Upstate and southern NC
mtns as we head into the overnight. This activity will likely
linger for a few more hrs, so I have a VCSH for the Upstate
terminals and KAVL thru the overnight. Moist ELY low-lvl flow
is expected to produce a low cloud deck over the next few hrs,
initially MVFR, but eventually dropping down to IFR. Confidence
is moderate wrt how low the cigs will go and how far they will
spread by daybreak. Will stick close to the model consensus,
with mostly MVFR and a brief period of IFR cigs this morning.
Assuming the low clouds develop, it will likely take until the
afternoon before they lift and/or scatter. Otherwise, expect NE
to ENE wind across the Piedmont sites, and mainly SE at KAVL.
With decent cloud cover thru much of the day over the Piedmont,
afternoon convection should mainly be confined to the NC mtns.
Thus, only KAVL will carry a PROB30 for TSRA today.

Outlook: Afternoon showers and thunderstorms with associated
restrictions are expected mainly across the mtns on Wednesday.
More widespread convection is likely across the entire fcst area
Thurs and Fri. Morning fog and low stratus are also possible,
especially in the mtn valleys each day.

&&

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

&&

$$

SYNOPSIS...RWH
NEAR TERM...JPT
SHORT TERM...Wimberley
LONG TERM...Wimberley
AVIATION...JPT