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341
FXUS62 KGSP 071757
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
157 PM EDT Mon Jul 7 2025

.SYNOPSIS...
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Hot and humid conditions continue through midweek featuring daily
afternoon and evening shower and thunderstorm chances. The heat
abates somewhat into the weekend but daily afternoon and evening
shower and thunderstorm chances continue.
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&&

.NEAR TERM /THROUGH TUESDAY/...
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As of 1100 AM Mon: As post-TC Chantal moves up the mid-Atlantic
coast thru the afternoon and evening, it is progged to be absorbed
into a weak sfc low centered in Ontario. With that development,
despite weak flow across the Appalachians aloft, a trough is setting
up over the Eastern Seaboard and into our CWA.  Vertical profiles
suggest no capping this afternoon, and indeed isolated ridgetop
convection initiated around noon as is typical for this time of
year. Per model omega and CAM reflectivity, dry air aloft seems to
be a limiting factor and keeps activity largely isolated thru the
afternoon. Best overall chance remains the mountains and foothills
where we retained isolated/scattered wording in the fcst. However,
given the trough a stray shower/storm cannot be ruled out in the
Piedmont, although the chance remains below 15% over much of that
area. Weak westerly shear could allow a few small clusters of
storms to develop. Can`t rule out an isolated wet microburst and
localized strong to severe wind gusts. Coverage should diminish
diurnally this evening.

A subtle cold front extends southwest from the aforementioned
sfc low into the mid-Mississippi Valley. A trough moving across
the northern Plains will help push the frontal features slowly
eastward by Tuesday. A sfc trough looks to remain east of the
Appalachians. While the front itself remains to our west through
peak heating Tue aftn, some degree of moisture pooling ahead
of it leads to higher PWATs and more midlevel moisture, both of
which make profiles more favorable for deep convection. The rest
of the pattern remains pretty similar to today. PoPs accordingly
tick upward such that 40-60% PoPs will be advertised over the
mountains, decreasing to 20-30% over the Piedmont. SPC continues
to highlight our eastern zones in Marginal Risk for damaging wind
on account of wet microburst potential associated with heavy water
loading and 2000+ SBCAPE in the afternoon. It could be argued the
severe potential will extend across more of the CWA, although such
storms are likely to remain isolated, and marginal-level risk is
appropriate. Temps will rise slightly warmer into the upper 90s
across much of the Piedmont, but thinking is that aftn mixing still
will bring dewpoints low enough to limit heat index to 100-104 in
most locations, so Heat Advisory does not look warranted.
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&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
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As of 200 PM Monday: A shortwave will propagate into the OH and TN
valleys on Wednesday, resulting in height falls over our area and
slightly lower thicknesses.  Its proximity will enhance forcing
across the area as diurnal heating supports SBCAPE of 1000-2000
J/kg.  Categorical PoPs exceeding 75-80% are forecasted across
the mountains and NC Piedmont, with likely PoPs of 60-75% over
much of Upstate SC and the GA Piedmont, where profile guidance
suggests a deeper mixed layer, higher LCLs, and subsequently
lower surface-based instability.  Bulk-shear values increase
slightly ahead of the trough but generally speaking, values are
not supportive of organized convection.  However, profile guidance
suggests that there will be sufficient mid- and upper-level dry
air to support isolated damaging microbursts.  PWs of 1.6-1.8"
and fairly unidirectional low- and mid-level flow support some
cell training capable of producing isolated areas of excessive
rainfall.  The suppression of the subtropical ridge and increased
cloud cover should reduce high temperatures a few degrees, though
most areas will likely peak at slightly above-normal temperatures
even if rain-cooled outflow arrives later in the afternoon.  While
afternoon mixing is expected to lower dewpoints a few degrees in
the afternoon, heat indices will likely approach the 100-103 range
in favored areas of the Savannah River Valley and the CLT metro.

With strong subtropical ridging in place over the Sargasso
Sea/western Atlantic and shortwave ridging over the Great Lakes,
there will be little eastward progression or deamplification of
the shortwave trough located just to our west over the TN Valley.
As such, expect similar unsettled weather and convective coverage
Thursday afternoon and evening.  Increasing moisture through the
column given persistent SWly flow and favorable storm-motion vectors
suggest a continued risk for isolated areas of excessive rainfall.
Bulk-shear values increase a bit further, approaching 20kts,
and despite tall and skinny CAPE profiles, a wet microburst
threat will continue where the strongest updrafts can develop.
High temperatures will fall a few degrees further compared to
Wednesday given thicknesses, cloud-cover, and convective coverage,
but this will only equate to highs near normal for mid-July.
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&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
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As of 200 PM Monday: The extended period will remain active as
we are generally sandwiched between subtropical ridging along the
Gulf Coast and the southern extent of the westerlies, which will
usher in rounds of weak shortwaves across the OH and TN valleys
and over the central and southern Appalachians through the period.
This pattern will support likely to categorical PoPs over the
mountains and foothills with chance PoPs over the Piedmont each
afternoon and evening.  Low-level moisture will continue to pool
across the area with flow taking a circuitous route from the western
Gulf of America, around the persistent Gulf Coast ridge, and into
the southern Appalachians; therefore, typical periods of heavy
rainfall can be expected, with isolated areas of excessive rainfall
possible.  Parameters are not supportive of a notable severe
weather threat any afternoon, with the typical isolated damaging
wet microburst being the primary concern.  High temperatures will
also remain fairly stable at near-normal values, with upper 80s
in the mountain valleys and lower 90s across much of the Piedmont.
Overall, pretty typical July weather is expected.
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&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
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At KCLT and elsewhere: Light winds mainly from the SW this
afternoon. KAVL could flip to NW at times this aftn but think
VRB is appropriate. Sct SHRA/TSRA mainly over the mountains and
foothills; chance is PROB30 range at KAVL, and nonzero but too low
to mention at KHKY/KGSP/KGMU. Lighter winds tonight, generally VRB
but possibly veering to WNW or NW otherwise. KAVL could see light
daybreak fog but not confident enough on restrictions to mention at
this issuance. Slightly better SHRA/TSRA chances around the region
Tue aftn after 18z, but a bit too low to warrant inclusion at KCLT.

Outlook: Typical summertime weather is expected thru late week,
with sct to numerous SHRA/TSRA mainly in the aftn/evening and fog
and/or low stratus possible each morning.
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&&

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

&&

$$

SYNOPSIS...JMP
NEAR TERM...Wimberley
SHORT TERM...JMP
LONG TERM...JMP
AVIATION...Wimberley