286
FXUS62 KGSP 310449
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1249 AM EDT Fri Jul 31 2026

.WHAT HAS CHANGED...
No significant changes for this forecast cycle.

Updated the Aviation Discussion for the 06z TAFs.

&&

.KEY MESSAGES...
1. Near-normal temperatures with unseasonably low humidity and
no threat for afternoon/evening storms continues today.
2. Another frontal system is expected to arrive from the west
this weekend, possibly stalling across our area early next week,
bringing back high rain chances, below-normal temperatures,
and some potential for locally heavy rainfall.

&&

.DISCUSSION...
Key message 1: Near-normal temperatures with unseasonably low humidity
and no threat for afternoon/evening storms continues today.

Weak shortwave ridging slides over the Appalachians today on the eve
of a notable pattern change. This will support another day of
continued average temperatures for late July in concert with
unseasonably low humidity. Climatologically dry air with sub-1"
PWATs is entrenched across the region with very dry forecast
soundings. A deep well mixed boundary layer extending up to ~800mb
will foster efficient mixing of surface dewpoints with values
falling off below 60 this afternoon and humidity values below 40%.
While a few shallow isolated cumulus clouds will be possible during
peak heating, the environment will be rather hostile to convective
development with no threat for traditional summer afternoon/evening
thunderstorms.


Key message 2: Another frontal system is expected to arrive from the
west this weekend, possibly stalling across our area early next
week, bringing back high rain chances, below-normal temperatures,
and some potential for locally heavy rainfall.

A notable pattern change commences on Saturday with a return to wet
and unsettled weather through the weekend and into next week. By
Saturday morning, a stout 600dam H5 ridge will be well established
over the Desert Southwest with active northern stream flow draped
from the Pacific Northwest through the Northern Rockies. A lead
shortwave trough will be dropping down the eastern flank of the
ridge across the Central Plains and into the Mississippi Valley. The
synoptic pattern also begins to amplify with a tall Bermuda high
building across the Atlantic, thus slowing the eastward progression
of the upper wave through the weekend. Height falls will gradually
overspread the Appalachians with an attendant surface low sliding
across the Ohio Valley and a surface frontal boundary pushing across
central Kentucky and Tennessee. Low-level mass response will
strengthen a 30-40kt low-level jet progged to translate across the
western Carolinas and northeast Georgia Saturday into early Sunday
morning. This will draw an anomalous plume of deep moisture into the
region with PWATs surging to 2-2.4", well north of the 90th
percentile for early August. Increasing moisture will also support
modest instability with 2000-3000 J/kg of surface-based CAPE. The
net result will be a rapid increase in rain chances through the day
Saturday and into the overnight hours. Guidance is in relatively
good agreement that a broad zone of convection will develop within
the deep moisture axis and shift east across the area. The presence
of the upper wave and low-level jet will likely support convective
elements through the overnight into early Sunday past the
traditional diurnal convective window. The main hazard of concern
will be for locally heavy rainfall and isolated to widely scattered
flash flooding from any slow moving/training storms within the high
PWAT environment and increased moisture transport within the cloud-
bearing layer. A secondary threat for isolated strong to severe
storms cannot be completely discounted, but the near-storm
environment is not overly impressive. DCAPE is forecast to be
underwhelming within such a moist environment, which is further
supported by near moist adiabatic mid-level lapse rates and
tall/skinny CAPE profiles. Nonetheless, a few isolated water loaded
downbursts could be realized.

The upper trough axis and surface frontal boundary approach the area
on Sunday and could kickoff another round of numerous to widespread
showers and storms, although the intensity of such is somewhat
uncertain owing to what will likely be widespread cloud cover. Given
the slow progression of the upper wave, attention will once again
need to be paid to any slow moving and training storms as the axis
of deep moisture will still be well established at least east of the
mountains.

Heading into next week, the 00z suite of guidance and their
respective ensemble members begin to diverge with respect to the
evolution of the synoptic pattern. There are indications that the
upper trough may evolve into a closed low and linger across the
Southern Appalachians as it becomes cutoff from the main northern
stream flow and sandwiched between the Desert Southwest ridge and a
building Bermuda high to the east. Regardless, at the very least a
general weakness between the two upper ridges will reside across the
region with a typical warm and humid late summer pattern featuring
daily diurnal convective chances. The weekend low-level jet and
plume of deep moisture will have shifted east at this point, thus
lowering the potential for a more focused flooding threat. However,
locally heavy rainfall and an isolated flooding threat can never be
ruled out with any summer storm, especially following several prior
days of expected rainfall.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: VFR conditions will prevail at all terminals
through the TAF period. A few high clouds will drift across the
region through tonight and Friday with a shallow afternoon cumulus
field between 5-6kft during the afternoon. High clouds will increase
in coverage overnight into Saturday morning as moisture streams back
into the region. Winds will be light and variable overnight and
generally out of the south/southwest during the day, but still light.

Outlook: Shower and thunderstorm chances and associated restrictions
return Saturday and continue into early next week. Low stratus
and/or fog will be possible each night starting Friday night, mainly
in the mountain valleys. More widespread low clouds and fog expected
Saturday night through Sunday morning.

&&

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

&&

$$

TW