544
FXUS62 KGSP 270700
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
300 AM EDT Mon Jul 27 2026

.WHAT HAS CHANGED...
Revised details about possible MCS activity affecting the area
early this morning or Tuesday morning. Similar thinking for severe
weather threat late Tuesday into Tuesday night.

&&

.KEY MESSAGES...
1. Severe weather remains possible Tuesday into early Wednesday
with thunderstorms developing ahead of a cold front.
2. A warming trend is expected through Tuesday, with slightly
cooler highs and lower humidity returning by Wednesday behind
the front.

&&

.DISCUSSION...
Key message 1: Severe weather remains possible Tuesday into early
Wednesday with thunderstorms developing ahead of a cold front.

The "ring of fire" pattern remains in place to start the week,
featuring a deep anticyclone over the Rockies/Plains and a trough
over the Great Lakes and East Coast. Multiple MCSs are ongoing in
the lower OH and TN valleys as of 2 AM. The most vigorous activity
will propagate southward and should miss our CWA to the west,
but a smaller cluster of storms which initially formed along the
warm front is advancing toward the NC mountains. These storms are
entering less unstable air and probably will not survive much past
the mountain spine, but could bring some locally heavy rain to the
Smokies and vicinity before daybreak. Cirrus debris is advecting
into the western CWA from the MCSs farther west, but that should
thin or advect out prior to peak heating today, so probably won`t be
a limiting factor in diurnal convection. However, thermo profiles
are quite dry above the PBL and weak capping is expected. The
remnant vortex generated by the morning MCSs probably will miss us
to the southwest as well, and after looking at a range of models
it appears any shortwave that might come into play Monday would be
a vortex from an upstream MCS (an MCV). Though with the profiles
being dry there may not be much possibility of convective initiation
even if an MCV were to track over our area. CAMs continue to be
largely devoid of any cells this afternoon so PoPs remain very low.

Extreme instability appears likely to form this afternoon in the
central Mississippi Valley; with the synoptic pattern remaining
very similar to yesterday, another MCS looks likely to develop
by this afternoon or evening, with NW`ly cloud layer flow and
forward-propagating Corfidi vectors suggesting one could make
a run at the NC mountains again tonight. The 00z NAM, 00z RRFS,
and 18z REFS all feature a decaying MCS or cold pool reaching the
TN/NC border early Tuesday morning. Given the timing and limited
MUCAPE, that doesn`t look particularly likely to produce severe or
hydro threats. The 00z HRRR appears to develop loosely organized
storms along the east flank of the cold pool which also reaches
the NC border near daybreak Tuesday. This results in some PoPs in
that area around that time; given the degree of shear can`t rule
out some cold pool driven strong to severe gusts even if storms
are not particularly tall. SPC Day 1 features a Marginal Risk in
that area, possibly just carried over from the old Day 2, but also
handling the outside chance of such development before 8 AM EDT Tue.

The possibility of the morning cold pool or MCS arrival continues
to be a source of uncertainty in assessing our severe potential
Tuesday, potentially delaying warming and keeping instability in
check. Assuming the cold pool is not a factor, Tuesday should be
a warmer and more unstable day. By Tuesday afternoon a cold front
should reach the Ohio Valley and thus the environment upstream
may be too stable to support an MCS; the most likely area of
development shifts south into TN instead, and an MCS forming there
could pass by to the southwest. Differential heating along a cold
pool or cirrus deck however could initiate storms, in addition to
the typical ridgetop convergence. The southward push of the cold
front looks to occur late in the day or in the evening, oriented
east-west across our area. The peak storm threat may be a bit after
peak heating or even after sunset. 0-6km shear looks likely to
be 30-40 kt, so supercell structures are not out of the question,
though shear vectors would appear to be somewhat parallel to the
front and we could see cells grow upscale into a QLCS. Damaging
wind remains the main threat though 1"-2" hail appears possible
with supercells. All this said, due in part to the uncertainty
posed by a morning cold pool, PoPs peak at only 20-40% over most
of the area south of I-40, but slightly higher south and east of
Charlotte since that area should have the most time to destabilize
ahead of the front. Northwest flow into the mountains could lead to
another round of activity developing Tue night or early Wed near
the TN border, but otherwise the convection should push south and
east by late evening.


Key message 2: A warming trend is expected through Tuesday, with
slightly cooler highs and lower humidity returning by Wednesday
behind the front.

Southwest flow ahead of the approaching front Tuesday should
maintain very humid conditions and with WAA, temps are expected to
trend warmer, into the lower-mid 90s across the Piedmont and near
90 in the mountain valleys. Heat index likely will rise to 102-105
(locally higher) in much of the Piedmont, while the valleys should
reach the mid-90s. There remains uncertainty due to the cold pool
or cirrus from a possible early morning MCS arrival, that could
wreck the warming necessary to reach these temperatures. Careful
evaluation of subsequent CAM runs will be needed before making
any decision about a possible Heat Advisory.

Behind the front, temperatures trend back to around climo on
Wednesday, with lower humidity that should keep indices below 100,
and much more stable conditions such that precip chances remain
small. Appreciably drier air filters in for Thursday that brings
PoPs and heat indices even lower despite temps being about the
same. The Upstate and NE GA, being warmer, actually see RH fall
to around 35% Thursday and Friday, exceptionally low for this time
of year.

The Western ridge / Eastern trough pattern lingers into next
weekend, though not unstable upstream so we do not expect MCS
threats. The next chances for rain/storms appear to be Saturday,
when a reinforcing shortwave or upper low rotates into the Eastern
trough, and induces return flow over the old front by then stalled
north of the Gulf Coast. PoPs develop Saturday and linger to Sunday,
with temps falling a bit below normal due to increased cloud cover.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Abundant surface moisture early this morning
with near-calm winds. Cirrus debris from upstream convection
will linger early this morning over the SC sites and possibly
KAVL, which makes radiation fog unlikely, though there could be
some clearing near daybreak so TEMPO still included for MVFR at
daybreak. KCLT and KHKY are likely to remain mostly clear, so TEMPO
IFR included at KCLT near daybreak and with KHKY already bouncing
up and down, TEMPO restrictions to start with prevailing LIFR nearer
daybreak. Monitoring KAVL for potential SHRA/TSRA early this morning
from small cluster moving thru East TN; that activity should weaken
as it passes the mountains but will stand by for AMDs if it makes a
run for KAVL. Otherwise, not expecting much SHRA/TSRA development
today, only diurnal cu forming near MVFR/VFR threshold before
mixing up to 045-060 near peak heating. Can`t rule out radiation
fog/stratus tonight though no mention yet made, with threat mainly
after 06z if at all; Light winds, with some variability due to
weak forcing and also due to lee trough expected to form this aftn.

Outlook: Decaying storm complex from TN could reach the mountains
around daybreak Tue but not likely to bring precip to TAF terminals
at that time. Strong to severe storms and breezy SW winds are
possible Tues afternoon/evening ahead of a cold front, but that
development could be limited by debris clouds or storm outflow from
the morning. Quieter and less humid weather Wed-Fri. Low stratus
and/or fog will be possible each morning, mainly in the mtn valleys.

&&

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

&&

$$

JCW