305
FXUS62 KGSP 300136
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
936 PM EDT Sun Jun 29 2025

.SYNOPSIS...
A typical summer pattern continues Monday with seasonable
temperatures and chances for afternoon and early evening
thunderstorms. A cold front approaches the area on Tuesday bringing
greater coverage of thunderstorms. Drier weather looks to return for
the holiday weekend behind the front.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 930 PM: Main changes this update were to touch up PoP trends
over the next few hrs, mostly based on current radar mosaic, with
CAMs doing poorly as usual with summertime pop-up storms. Swirl
seen on water vapor imagery associated with shortwave trough, more
or less stationary to our south. Given that providing weak lift
and reinforcing S to SE flow in low levels, think best chance for
redevelopment this evening will be generally outside the mountains,
in areas ahead of remaining outflow boundaries between I-40 and
US 74 in the NC Piedmont and in the Savannah River Valley. A stray
mountain shower however is possible in the next hr or two. Chances
going below slight-chance around midnight.

Expect clearing skies and light winds overnight. Mountain valley
fog is likely with patchy fog elsewhere, especially near bodies
of water or locations that had heavier rainfall. At this update,
saw fit to include a mention of fog near Clemson and Liberty where
heavy showers moved in late in the day, and fog is climatologically
more favored. Elsewhere confidence too low to put in a mention
at this time. Lows near normal mountains and a few degrees above
normal elsewhere.

Monday looks to be a near carbon copy with good coverage of
convection developing across the mountains around noon and scattered
convection elsewhere. Expect a near carbon copy with the severe
downburst and heavy rain potential with a very unstable air mass,
light bulk shear, moderate DCAPE, and high PW values. Highs across
the mountains will be near normal and a few degrees above normal
elsewhere.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 1225 PM Sunday: A northern stream trough will swing across the
Great Lakes region and into New England on Tuesday while another
upper low associated with a Tropical Upper Tropospheric Trough
drifts along the southeast coast. Broad Bermuda ridge will also
extend into the Coastal Plain which will further promote deep-layer
southwest flow across the region. Plentiful deep moisture will be
present within this regime with a surface cold front approaching the
area from the northwest within the trough axis. Moisture pooling
ahead of the frontal boundary in concert with weak, but non-zero,
forcing will promote numerous to widespread mainly diurnal
thunderstorms across the area on Tuesday. Weak troughing and the
nearby position of the front may even support several storms
continuing into the overnight beyond the traditional diurnal
pattern. Forecast soundings reveal traditional summer profiles in
the southeast with very tall/skinny CAPE and a lack of drier air.
The result is poor lapse rates, weak DCAPE and a lower surface delta
ThetaE. Clusters of storms and/or linear segments will likely
organize along composite cold pools and a couple strong to isolated
severe storms cannot be ruled out with the main threat being
isolated wet microbursts. The boundary itself slowly drops into the
area Tuesday night into Wednesday with another round of diurnal
showers and storms Wednesday afternoon and early evening.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 1245 PM Sunday: A second shortwave trough drops across the
Great Lakes Thursday with weak northwest flow setting up over the
Southern Appalachians in the wake of the first trough axis. This
should help to slowly push the frontal boundary across and
eventually south of the area. How long this takes and exactly how
far south it ends up remains to be seen. If progress is slower at
least isolated to widely scattered diurnal storms will remain
possible across southern portions of the area on Thursday and
potentially Friday. Most of the area should see the arrival of drier
air, however, with PWATs falling to 1-1.25" within lower ThetaE air.
Historically, PWATs this low are unfavorable for summer diurnal
pulse convection although an isolated storm or two can never be
ruled out across the mountains. Relatively dry weather may continue
through the holiday weekend, but deeper moisture will eventually
return and it`s arrival will be tied to an increase in rain chances -
 whenever that ends up occurring.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Isolated SHRA/TSRA may linger around the
region thru about midnight, with mostly clear skies and very
light SW if not calm winds the remainder of the night. Some
mountain valley fog is possible but not necessarily at KAVL;
only mention is in TEMPO. Can`t rule out some patchy fog in the
terminal area where heavy rain fell today; KGMU was the only TAF
site which had heavy rain, but still not confident enough to
mention there. Diurnally driven SHRA/TSRA expected again Monday
in similar fashion to Sunday. Low VFR cu break out late morning
to midday with PROB30 or TEMPO during peak heating. Slightly
stronger winds expected in the afternoon compared to the last
couple of days, and can`t rule out an occasional gust to 15 kt
or so.

Outlook: Daily chances for afternoon and evening showers and
thunderstorms through Wed. Fog and/or low stratus possible each
morning in the usual mountain valleys as well as near lakes and
rivers. Drier air may move in Thu inhibiting convection for a
couple of days.

&&

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

&&

$$

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