071
FXUS62 KGSP 152337
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
737 PM EDT Mon Sep 15 2025

.SYNOPSIS...
High pressure keeps much of South Carolina and Georgia dry
through mid week while North Carolina gets some rain Tuesday and
Tuesday night as a low pressure system moves north along the North
Carolina coast.  The low weakens Wednesday and Thursday as it moves
away from our region.  High pressure returns and remains in place
through the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 730 PM Mon: PoPs were bumped up to reflect latest radar
trends, as convection coverage is greater than expected across
much of the mountains, foothills and western Upstate. A few
garden-variety thunderstorms have also developed. Given the modest
CAPE of around 1000 J/kg and low DCAPE, not expected any strong
or severe storms this evening. The latest HRRR has come in pretty
active, with a lot of coverage across the Upstate and NE GA thru
the evening. This seems overdone, but another update to PoPs may
be needed this evening.

Otherwise...Weak sfc ridge extends down the Appalachians from
eastern Canada. Coastal low now centered SE of Cape Hatteras
and producing breezy/gusty conditions across the eastern halves
of NC/SC. Upper low seen on water vapor imagery centered near
Fayetteville; vort lobe rounding that feature is distinctly
shown west of I-95 and will rotate westward, possibly providing
lift for some late-day or evening convective development. An
inversion associated with the ridge and/or on periphery of the
coastal low should keep instability in check and keep convection
relatively shallow, SBCAPE is shown upward of 1000 J/kg on SPC
mesoanalysis, which may be a little overdone. However, with at
least slight instability and low-end CAM response, we retain a
slight-chance PoP mention in parts of the mountains--mainly along
the east-facing Escarpment where slight upslope lift also plays
a role. Indeed as of this writing a few pinprick showers are seen
on base reflectivity. Storm motion will remain generally northerly
so if a shower or storm does manage to survive long enough, some
sprinkles could reach the foothills south of the Escarpment. CAM
response suggests shallow convection and highly isolated showers
could continue in some of the western CWA tonight as low-level
convergence west of the low kicks off elevated parcels. High
altitude cloud cover is expected to increase although, similar to
Mon morning, but not likely enough to inhibit mountain valley fog.

Low to midlevel winds back to a more northerly or NW`ly direction
late tonight and remain so Tuesday as coastal low shifts onshore
over eastern NC. Some degree of convergence could promote
development of a few showers in the SW mountains and parts of
the upper Savannah Valley which would track S to SSE into our
northern GA/SC zones. In the NC Piedmont, although models are
not in great agreement as to timing or depth, low level flow
will remain northeasterly and effectively bring in a backdoor
front, with sufficiently deep moisture to expect light precip to
result. Altogether, chance-range PoPs are forecast over much of
the western mountains and Escarpment, as well as northeast of US
321. With more cloud cover expected and the CAA, max temps trend
below normal over much of NC and generally a few degrees cooler
elsewhere.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 1:25 PM EDT Monday: The short-term forecast picks up at 00z
on Wednesday with a short-lived Rex block gradually breaking down
over the eastern CONUS. By early Thursday, the block has pretty much
dissipated with broad upper ridging still in place across the eastern
CONUS. At the surface, broad Canadian high pressure will be centered
over Nova Scotia while a weak coastal low will be nearly stationary
over the NC Coast. Over the next couple of days, the sfc low will
gradually drift northward and up the Atlantic Coast. By the end of
the period late Thursday the low is expected to move further NE and
dissipate out over the Atlantic putting our area back under weak high
pressure. Overall, the fcst continues to trend drier with only a slight
chance for precip over our NE zones early Wednesday. For the rest of
the period, PoPs are less than 20%. I still expect temperatures to
start out a few degrees below normal on Wednesday and warm to a few
degrees above normal on Thursday.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 1:10 PM EDT Monday: The extended forecast picks up at 00z on
Friday with broad upper trofing amplifying over southern Quebec as
another closed upper low spins over the northern Plains. Over the
weekend, the upper trof is expected to move off the coast of Nova
Scotia and remain well to our north. At the same time, the upper low
will drift eastward towards the Great Lakes and open back up to the
mean flow. Upper ridging is expected to remain over the Southeast
thru the weekend, though it will likely flatten by late weekend.
At the sfc, our area will be under weak high pressure as the period
begins late Thurs. Another sfc low is expected to develop somewhere
over the central/northern Plains on Friday and then move towards the
Great Lakes. At the same time, another robust Canadian high will mi-
grate SE and over New England. This high is expected to prevent the
sfc low from advancing very far eastward. Instead, most of the long-
range guidance has it dissipating somewhere over the western Great
Lakes by late weekend. This pattern will likely keep high pressure
wedging down over our area thru the weekend, resulting in drier con-
ditions than previously fcst. Temperatures are still expected to start
out about a category above normal on Friday and cool over the weekend
to just below climatology.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Coverage of convection is much higher than
earlier guidance was indicating across the mountains and into the
central and western Upstate. Will add VCSH for the upstate TAF
sites, and a TEMPO for some MVFR SHRA at KAVL to start the 00z
TAFs. Some of the CAMs show showers continuing to bubble up across
the area overnight, but confidence is low. Plenty of mid and high
clouds will linger well into the night, thanks to a coastal low
just to our east. Some clearing across the mountain valleys may
allow fog to form. Otherwise, VFR conditions expected. Similar
conditions expected again Tuesday, with scattered mountain showers
and isolated TS. Will carry a PROB30 for SHRA at KAVL tomorrow
aftn. Some of this activity may try to work into the Upstate again,
but confidence too low to add any mention for now. Wind will be
light out of the N/NE tonight thru Tuesday morning, then pick up
some in the aftn, especially at KCLT, where low-end gusts can
be expected in the aftn. Some MVFR clouds may pivot around the
coastal low and approach KCLT Tuesday evening.

Outlook: Rain chances will stick around through mid-week with
periodic MVFR restrictions possible at times. Some mountain valley
fog will remain possible where clouds do not inhibit nocturnal
radiation. Drier conditions should return by Friday.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...ARK/Wimberley
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...ARK