310
FXUS62 KGSP 181041
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
641 AM EDT Sat Jul 18 2026

.WHAT HAS CHANGED...
Updated the aviation discussion for the 12Z TAFs.

&&

.KEY MESSAGES...
1. Hot and humid conditions linger through Sunday with heat index
values ranging from 100 to 105 degrees each afternoon. Slightly
cooler temperatures return next week which should keep heat
indices mostly below 105 degrees.
2. Coverage of mainly diurnal showers and thunderstorms increases
through Sunday. A few storms could become severe both days
with damaging winds the main hazard. Mainly diurnal shower and
thunderstorm chances linger through Monday with a brief lull in
activity on Tuesday before a cold front brings the potential for
another round of severe weather on Wednesday.

&&

.DISCUSSION...
Key message 1: Hot and humid conditions linger through Sunday with
heat index values ranging from 100 to 105 degrees each afternoon.
Slightly cooler temperatures return next week which should keep heat
indices mostly below 105 degrees.

Better convective coverage and associated cloud debris, along with
lower thickness values, will allow for slightly cooler temperatures
this weekend ranging from the low to mid 90s. However, dewpoints
will be more elevated, ranging from the low to mid 70s. This will
allow hot and humid conditions to linger through the weekend with
triple digit heat indices expected each afternoon east of the
mountains. Union County NC looks to be the only location with
significant coverage of 105 heat index values today. Isolated
locations elsewhere could briefly see 105. Therefore, have issued a
Heat Advisory only for Union NC for now. Sunday will be a few
degrees cooler which should keep any 105 heat index values limited
to isolated locations.

Individuals should prepare for elevated heat through the weekend.
Stay hydrated, take frequent breaks in air-conditioned or shaded
areas, and never leave children or pets unattended in vehicles.


Key message 2: Coverage of mainly diurnal showers and thunderstorms
increases through Sunday. A few storms could become severe both days
with damaging winds the main hazard. Mainly diurnal shower and
thunderstorm chances linger through Monday with a brief lull in
activity on Tuesday before a cold front brings the potential for
another round of severe weather on Wednesday.

An upper trough will dig into the Great Lakes region and the
northeastern CONUS through Sunday as a cold front approaches the
area. Better moisture advection ahead of the front and increasing
low-level convergence will support an uptick in coverage of
convection both days. With sbCAPE reaching the 2,000-3,000 J/kg
range during peak heating and deep layer shear increasing slightly
to 15-25 kts each day, convection should become more organized.
Steep low level lapse rates and high PW values will create a threat
for damaging downbursts. Thus, the SPC Outlooks showing a Marginal
and Slight risk across the GSP CWA for both days appear warranted.

Convective chances linger through Monday but confidence on the
severe threat is low at this time. Should see a brief lull in
coverage on Tuesday before a cold front brings better convective
chances back Wednesday. Strong to severe storms are possible ahead
of the front on Wednesday, but confidence on the severe threat this
far out remains low.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: IFR stratus near KAND could create a ceiling
until 14Z. Mountain valley fog should remain away from KAVL this
morning. Otherwise, VFR through the morning with Cu developing. A
better chance of convection across the board this afternoon and
early evening. PROB30s are in place for all locations. SW winds pick
up during the day with low end gusts, NNW at KAVL. Convection
diminishes during the evening with VFR and light winds. Another
round of mountain valley fog/stratus expected overnight.

Outlook: Good coverage of afternoon/evening SHRA/TSRA continues
through Monday with lower chances on Tuesday before increasing again
Wednesday. Low stratus and/or fog will be possible each morning,
mainly in the mountain valleys.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Heat Advisory from noon today to 8 PM EDT this evening for
     NCZ082.
SC...None.

&&

$$

RWH