Mc Connells, South Carolina Weather Forecast Discussion

278
FXUS62 KGSP 221752
AFDGSP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
152 PM EDT Mon Sep 22 2025
.SYNOPSIS...
Scattered afternoon and evening showers and thunderstorms are
expected, mainly over the mountains and foothills through Wednesday.
A cold front reaches our region late in the week with showers and
thunderstorms becoming more widespread ahead of the front Thursday
into Friday.  Temperatures will remain above normal for this time of
year ahead of the front then cool to near normal over the weekend
with drier weather.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 1251 PM EDT Monday: Another afternoon with a healthy cu
field over the foothills/western Upstate/northeast Georgia, where
the low level moisture was the best. Some enhanced cu were noted
on ridgetops, though nothing was showing on radar just yet. The
SPC mesoanalysis shows a modest 1000-1500 J/kg of sfc-based CAPE,
which should be enough to fuel some shower activity, and maybe a
thunderstorm, mainly along the TN border down to the Smokies and
perhaps down across the Nantahala Mtns as well. Nothing too out of
the ordinary. The Marginal Risk on the Day 1 Convective Outlook
was noted just west of the mountains, but this does not appear
to be a case where closeness counts. The guidance depicts a sharp
gradient in buoyancy this afternoon along the TN border region, so
the lack of buoyancy across the NC mtns will be a strongly limiting
factor. All the decent forcing moves past well to our northwest
as well. Temp/dewpt were running along nicely, so no need for
updating the high temps, which will be seasonally warm once again.
The afternoon convection should die off with the loss of heating
this evening, leaving us once again with another overnight with
the same air mass. Persistence still looks like a good forecast,
thus expect yet another round of locally dense mtn valley fog. For
Tuesday, the old weak sfc ridge finally breaks down for good as a
short wave moves across the region through the day. Normally this
sort of forcing would be a trigger for deep convection, but the
air mass east of the mtns never really recovers much in spite of
the sfc ridge breaking down, and the limited instability doesn`t
do much for our chances of precip east of the mtns. Sure, the mtns
will have a customary chance, but the CAMs show very little east of
the Blue Ridge, with the only decent possibilities shown along/N
of I-40 in the afternoon. A bit of warm advection will help push
temps back up to ten degrees above normal. Nowhere near a record,
but definitely warm for the first full day of autumn.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 127 PM EDT Monday: Model guidance are in good consensus
with developing a digging positively-tilted trough across the
central CONUS that will help induce surface cyclogenesis and
send a deepening parent low into the Great Lakes region and OH
Valley Wednesday into Thursday. A trailing cold front will shift
towards the area as a result by Thursday. Another round of diurnal
convection is expected Wednesday across the mountains, but with
the Bermuda high still having some influence and suppressing the
atmosphere, the rest of the area should remain mostly dry on
Wednesday. A strong pull of WAA ahead of the front will commence
and allow PWATs to rise towards 1.50"-2.00+" across the area, ahead
of the front. The better shear and forcing will reside with the
parent low as it shifts towards the Northeast on Thursday. With that
being said, CAPE values have risen slightly with deep layer shear
on the order of 25-35 kts. Some organized convection may develop,
leading to a low-end severe threat Thursday afternoon. However,
with guidance indicating more of an open wave rather than a cutoff
upper low, the cold front will have a better chance at making
a quicker fropa, cutting down on the overall QPF response. The
best timing for rainfall still looks to be around Thursday and
Thursday night before the front makes its way into the area by
Friday. Low confidence on any potential hydro or severe concerns
at this time. The last real day of heat will come Wednesday as very
warm thicknesses remain in place without any subtle height changes,
with partly to mostly sunny skies and temperatures 4-8 degrees above
normal for afternoon highs. Extensive cloud cover and precipitation
will knock temperatures back to near-normal values on Thursday.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 141 PM EDT Monday: The short-term cold front should make
a fropa during the day Friday, with not much fanfare following
the fropa. However, guidance have trended towards developing a
weak cutoff low somewhere in the southeastern CONUS, closer to
the Gulf Coast region. This may keep lingering precip chances
around over the weekend, but too far out for much detail beyond
that. Confidence is higher and that temperatures will cool off
nicely with lower thicknesses in place and the potential for
lingering cloud cover and precip going towards the end of the
forecast period. Temperatures will likely run around or slightly
below normal through much of the forecast period.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Still a few areas close to the Blue Ridge
Escarpment where the cloud base was around 030, thus a few places
that could have a temporary MVFR ceiling over the next hour, but
the cloud bases should all be in the VFR category by 19Z. The CAMs
suggest less coverage of showers and storms over the mtns thru this
evening, so the PROB30 at KAVL was dropped back to a VCSH as the
better chances for storms should stay on the TN side of the mtns. As
for tonight, will go to the well one more time given the lack of air
mass change, but this time I went straight to a prevailing LIFR by
09Z rather than dance around with a TEMPO. The sun isn`t as strong
these days, either, and the fog hasn`t been burning off until 14Z
or so, thus the delay in improvement. Tuesday looks similar again,
with precip chances mainly over the mtns, though wind should come
around to S to SW for the afternoon as a short wave moves through.
Outlook: Mountain shower and thunderstorm chances through midweek,
then better chances for restrictions with a front Thursday and
Thursday night.  Fog and stratus possible each morning in the
mountain valleys.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...DEO
NEAR TERM...PM
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...PM

NWS GSP Office Area Forecast Discussion