982
FXUS62 KGSP 181746
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
146 PM EDT Mon Aug 18 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 TUESDAY/...
As of 1234 PM Monday: Satellite imagery shows enhanced cu on
the ridgetops at midday, so it shouldn`t be too long before we
see some radar returns across the mtns. The mesoanalysis shows a
bit less sfc-based instability compared to the previous few days,
generally 1500-2500 J/kg, but that`s still enough to fuel a chance
of showers and storms mainly over the mtns and foothills thru the
afternoon. A weak boundary analyzed across NC should provide just
enough focus, and would favor putting at least isolated storms
across all of northeast GA and the Upstate at some point. The
northeasterly flow will tend to concentrate the convection over
the western Upstate and southern mountains/northeast GA mountains
late in the afternoon. Our severe chances are relatively low,
but an isolated storm that produces damaging wind gusts could
happen given sufficiently low dCAPE. Temp/dewpt trends look good
again. This afternoon should be the hottest of the string, but
new guidance still keeps the dewpoint low enough to keep the heat
index below Advisory criteria.

The weak front should continue to drift south this evening while a
large sfc high over Quebec noses down east of the mtns in wedge-like
fashion overnight. Most of the convection should diminish late this
evening with the loss of heating, but guidance shows increasing
low level moisture on a developing ENE flow late tonight that gets
pushed upslope against the Blue Ridge Escarpment in NC. The CAMs
agree in redeveloping more shower activity on/near the Escarpment
in NC into the early morning hours, possibly moving southwestward
over the nrn Upstate/northeast GA toward daybreak Tuesday if it
can get that organized. This poses an outside threat for heavy
rain and localized flash flooding if cells can get anchored near
the Escarpment for long enough. Precip probs are kept overnight
in these areas, but the rest of the fcst area should have a low
prob. Low temps should be seasonally mild. As for Tuesday, 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 northeast 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. Precip probs should be above climo over the mtns
of northeast GA and southwest NC because of enhanced low level
convergence, but below slight chance over the NW Piedmont where
drier air advects in from the northeast. Temps are expected to be
a category on the cool side of normal because of the cloud cover.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 1225 PM EDT Monday: The forecast area remains situated between
Erin moving north off the East Coast, and the trough that pick it
up, and the center of a ridge over the 4 Corners region. This
results in a general northerly flow over the area with some weak
short waves dropping south through the flow. Drier air and
subsidence associated with Erin will limit diurnal convection to
mainly the mountains on Wednesday where moisture lingers ahead of a
weak front. Moisture returns and subsidence abates across the area
Thursday as Erin moves away from the coast. This will allow
instability to develop with a better chance of diurnal convection
across the area but still favoring the mountains. The severe storm
and flood threat is very low both days, but non-zero especially on
Thursday. Temps will be around normal Wednesday then fall a few
degrees Thursday.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 1245 PM EDT Monday: An upper low moving out of Canada to the
Great Lakes by Sunday helps knock down the influence over our area
from the Western CONUS ridge. This results in an initial quasi-zonal
flow followed by a weak trough. The low moves east on Monday with
quasi-zonal flow returning. At the surface, weak high pressure
slowly traverses the area through Saturday. A weak cold front
crosses the area Sunday with high pressure building in behind the
front on Monday. Moisture and instability will be sufficient for
continued mainly diurnal convection, once again favoring the
mountains, Friday through Sunday. Temperatures will be 5 to 10
degrees below normal with Saturday the coolest day. With drier and
more stable air moving in behind the front on Monday, only some
isolated diurnal convection expected over the mountains. Temps will
be around 5 degrees below normal.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Deep convection has been slow to develop
today, but there`s sufficient instability to fuel the development
of showers and storms over the mtns and foothills, so those
terminals get at least a VCTS or VCSH. Otherwise, a cu field has
developed. Some terminals could have a brief bkn VFR ceiling, and
that will be included at KCLT. Wind will be generally light NE. Most
of the convection will diminish with sunset, but a developing moist
easterly flow could keep the convection going on the east-facing
Escarpment in NC into the early morning hours, thus a PROB30 has
been included at KHKY. Will keep it out of other terminals unless
indicated by later guidance. The moist easterly flow is expected
to either advect westward or force the development of a low cloud
deck after midnight, intially MVFR, but eventually dropping down
to IFR. This could go either way...down to LIFR or not at all...so
not much detail is provided due to low confidence. Assuming the
low clouds develop, it will take until the middle part of Tuesday
to start lifting and scattering. The fcst optimistically improves
most terminals to VFR by the end of the period. Wind should stay NE.

Outlook: Afternoon showers and thunderstorms with associated
restrictions are expected mainly across the mtns Wed. More
widespread convection expected at all terminals Thu-Fri. Morning fog
and low stratus are also possible, especially across the mountain
valleys each day.

&&

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

&&

$$

SYNOPSIS...RWH
NEAR TERM...PM
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...PM