541
FXUS62 KGSP 282359
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
759 PM EDT Sat Jun 28 2025

.SYNOPSIS...
A typical summer pattern continues through the weekend and into
early next week with seasonable temperatures and daily chances
for afternoon and early evening thunderstorms, especially over
the mountains. A cold front approaches the area on Tuesday with
thunderstorm chances increasing area wide. Drier weather may return
late next week heading into the Independence Day holiday if the
front is able to push south of the area and allow drier air to
settle across the region.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 745 PM: Parts of the Lakelands and eastern Upstate remain the
only places not overrun by outflows. A few storms do continue in the
Smokies and Snowbirds but those are expected to fizzle diurnally
in the next hr or so. The Upstate outflows are still kicking off
new updrafts and diurnal decline may take longer, perhaps as late
as midnight. A new storm producing a damaging downburst can`t be
ruled out if it can become tall enough owing to modest DCAPE.

Expect another round of mountain valley fog when convective debris
dissipates. Can`t rule out patchy fog elsewhere. Lows near normal
mountains and a few degrees above normal elsewhere.

Although guidance is showing the air mass won`t be as unstable
Sunday, it will still be moderately unstable. PW values remain
high with even less mid level dry air leading to lower DCAPE and
sfc delta theta-e values. However, forcing will be enough for
more diurnal convection favoring the mountains and foothills with
scattered coverage elsewhere. Severe chance is lower but heavy rain
chance higher given the previously mentioned conditions. Training
or anchoring of cells will be possible once again. Highs will be
near normal across the mountains and a few degrees above normal
elsewhere.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 1221 PM Saturday: The forecast continues tomorrow night with
broad Bermuda ridge extending across the Atlantic and into the
southeast coast. Farther upstream, a northern stream trough will be
swinging across the Canadian Prairies and Northern Plains. The trough
is progged to slide across the Midwest on Monday and across the
Great Lakes into New England on Tuesday. Weak deep-layer southwest
flow will keep a moist sub-tropical airmass entrenched across the
area with PWATs of 1.75-2". A persistence forecast seems likely on
Monday with scattered to numerous diurnally driven thunderstorms
with the greatest rain chances across the mountains. Outflow
boundaries pushing out of the mountains may initiate new scattered
convection mainly along and north of I-85 with generally isolated to
widely scattered coverage farther south/east. The forecast turns
wetter on Tuesday as the previously mentioned trough passes north of
the area and drags a cold front within the trough axis towards the
area. Deep moisture pooling ahead of the boundary along with a
slight uptick in flow/weak forcing will prove sufficient to
instigate numerous to widespread afternoon/early evening storms
across much of the area. Storms may loosely organize into
clusters/linear segments along composite cold pools. As with any
summer convection, a few strong to isolated severe storms cannot be
ruled out with the main threat being wet microbursts. The
environment won`t be overly conducive to damaging winds with poor
lapse rates, DCAPE, surface delta ThetaE and vertical totals - thus
any severe threat should remain fairly isolated.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 1232 PM Saturday: The latest suite of global model guidance is
in fairly good agreement that the frontal boundary will slide into
the area on Wednesday with another day of fairly high coverage of
diurnal thunderstorms. By Thursday, the boundary begins to push
south and east of the area with much lower ThetaE air arriving in
its wake. This would shunt the greatest rain chances south of the
area with a return to a mostly dry forecast. Depending on how far
south the boundary makes it, the forecast may remain dry through the
4th of July holiday weekend. Of course a few isolated showers/storms
can never be ruled out over the mountains even in a post-frontal
airmass. Should the boundary stall over or near the area, however,
the forecast would stay active through the holiday weekend. Current
model trends support the drier forecast, so will keep rain chances
in line with the national model blend with only isolated chances
being advertised.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
At KCLT: Outflow boundaries south of the field will allow storms
to persist nearby in the first hr or two of the period, so a rare
mention of VCTS is included. A direct TS hit is not out of the
question but this is handled with TEMPO. Winds will be mainly ENE
within cold pool, but should return to light SW by late evening as
cold pool mixes out. Fog too unlikely to mention at daybreak. Sunday
expected to evolve similarly to Saturday in terms of low VFR cu
lifting and with scattered TSRA warranting PROB30 in the afternoon.

Elsewhere: Outflows have worked over all the terminals and TSRA
chance is near zero, except KAND which still has some cu bubbling at
issuance time. Mostly light/VRB winds overnight but KHKY/KGMU/KGSP
still seeing some effects of cold pool winds. Remaining overnight
clouds will be just cirrus convective debris. Mountain valley fog
likely although KAVL did not get a direct TS hit, and guidance has
backed off earlier depiction of IFR. Now prevailing MVFR vsby with
IFR level SCT deck. KHKY had +RA very nearby and felt TEMPO was
warranted for same conditions as KAVL. Low VFR diurnal cu develop
by late morning Sun, winds coming up from the SW, both similarly
to Sunday. Severe wind potential lesser though +RA more likely
where TS develop. PROB30 for all sites.

Outlook: Daily chances for afternoon and evening showers and
thunderstorms into next week. Fog and/or low stratus possible
each morning in the usual mountain valleys as well as near lakes
and rivers.

&&

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

&&

$$

SYNOPSIS...TW
NEAR TERM...RWH/Wimberley
SHORT TERM...TW
LONG TERM...TW
AVIATION...Wimberley