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057
FXUS62 KGSP 090110
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
910 PM EDT Tue Jul 8 2025

.SYNOPSIS...
Hot and humid conditions will cool closer to normal late
this week with numerous afternoon and evening showers and
thunderstorms. The heat builds again from late in the weekend into
early next week as an upper ridge forms, but daily afternoon and
evening shower and thunderstorm chances continue.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
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As of 730 PM Tuesday: The convection was winding down across the
region, what with a large outflow boundary running off to the
northwest from the earlier convective complex over the Coastal
Plain. The air mass over the northern Upstate and NC Foothills
was relatively inhospitable with lower dewpoints yielding only
1000 J/kg of CAPE. Not much of a surprise that the outflow was
unproductive. The ongoing convection over the mtns is still expected
to weaken and dissipate in the hour or two after sunset. Temps
were modulated by the storm outflows, but should revert to the
expected trend by the early morning hours.

Otherwise...a broad Bermuda ridge extended into the southeast
states with a northern stream trough sliding across the Great Lakes
region. The pattern changes tomorrow as the previously mentioned
trough slides across the Ohio Valley and helps to draw a plume of
deeper moisture into the area with PWATs surging to 1.5-2" across
the area. Weak height falls overspreading the region ahead of the
trough axis in concert with a very warm and moist airmass will
foster a much better environment for diurnal convection. Numerous
to widespread thunderstorms are expected across much of the area,
especially northeast of the Savannah River Valley. This will help
keep temperatures a few degrees cooler, but at the expense of a
noticeably more humid airmass. As with any summer thunderstorms,
a few strong to isolated severe storms with wet microbursts cannot
be ruled out, but meager lapse rates and poor DCAPE will generally
preclude a greater threat for organized damaging wind. Storms will
also produce very efficient heavy rain with isolated pockets of 1-3"
in short amount of time possible. This may lead to several instances
of nuisance/minor flooding of low-lying and poor drainage areas,
especially along and east of I-77 closer to the main plume of
deep moisture. Should this type of rainfall occur over an urban
area, such as the Charlotte metro, isolated flash flooding will
be possible. Given the isolated nature of locally heavy rainfall
and uncertainty as to where it would occur, will hold off on any
hydro headlines at this time.
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&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of noon Tue: Cyclonic flow continues over the eastern US through
the short term period as deep shortwave moves across Ontario/Quebec.
Sufficient shear and forcing is expected to allow diurnally
initiated convection to continue through Wednesday evening, so
PoPs diminish only slowly at that time.  Model consensus suggests
an embedded, more compact shortwave will move across the mid-MS
Valley Thursday and be invof the southern Appalachians Friday.
This feature may be enhanced by diurnal convection upstream of our
area, and accordingly there is spread among models as to where
it will be located Friday. Regardless the upper pattern should
be more favorable for diurnal convection than what we typically
see this time of year. Following multiple days of SW flow ahead
of the trough axis, PWATs will be above normal (+1.2 to +1.5 SD),
generally a bit higher Thu compared to Fri as the main trough axis
shifts east a bit.  Altogether this results in PoPs in the likely
to categorical range each day, once again being higher Thursday.

0-6km shear is shown to increase ahead of the compact shortwave,
perhaps exceeding 30 kt Thursday or Thursday night. There appears
the possibility of an organized band of convection developing with
the wave late Thursday in our western CWA, which might result in
a damaging wind threat more widespread than from typical summer
pulse storms; that said, moist profiles that day may limit cold pool
formation and mitigate that threat to some degree. Despite the deep
layer shear, flow will be unidirectional and Corfidi vectors short,
so training or backbuilding may occur. Combined with the PWATs,
an above-average threat of localized torrential rainfall and flash
flooding will persist.

Max temps will be near normal and heat index will remain below
advisory criteria.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 1245 PM Tue: Axis of the Canadian trough will be east of the
area Friday night and 500mb heights slowly rise thru the weekend.
That results in a gradual warming trend, with daily max temps
a few degrees above normal for Sunday and Monday. Heat index
accordingly will rise closer to, but not quite reaching, Heat
Advisory criteria in parts of our Piedmont southeast of I-85. With
respect to convection, while we may lose the enhancing effect
of the trough, ensemble CAPE and CIN don`t change much Sat-Mon
afternoons compared to Friday. Furthermore most deterministic runs
and ensemble members depict another trough in the Midwest circa
Sunday, suggesting a front will approach the CWA from the west
by Monday. There is however spread as to the advancement of any
front east of the Appalachians between the GEFS and EC Ensemble,
keeping confidence low.  For now, it seems reasonable to expect only
a small decline in daily PoPs for this period, still warranting
likely values for the mountains each afternoon and a solid chance
(30-45%) for the Piedmont.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
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At KCLT and elsewhere: Dealing with a few thunderstorms right
around KAVL at issuance time, so we will hang onto a TEMPO for TSRA
there. Otherwise, the outflow boundary has passed NW across KCLT so
they should be quiet, and the Upstate/foothills terminals are not
unstable enough to support new storm development. Thus, expect a
quiet VFR night with only some debris clouds. Will plan to add some
MVFR fog restrictions back in at KAVL in the pre-dawn hours once
the ongoing storms dissipate. That brings us to Wednesday, which
looks quite a bit more active than today, what with more humidity
returning and a more favorable upper level environment for storm
development. Daytime heating should push the buoyancy up high enough
to allow for numerous storms mainly in the afternoon and evening,
though the models indicate a later than usual development time. For
that reason, we will go with a strategy that employs a PROB30 first
in the mid/late afternoon and a TEMPO in the early evening. There
will be some potential for strong thunderstorm outflows, so expect
variable flight conditions and strong gusts near storms.

Outlook: Typical summertime weather is expected into the
weekend, with scattered to numerous thunderstorms mainly in the
afternoon/evening and fog and/or low stratus possible each morning.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...PM/TW
SHORT TERM...Wimberley
LONG TERM...Wimberley
AVIATION...PM