541
FXUS62 KGSP 021810
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
210 PM EDT Sat Aug 2 2025

.SYNOPSIS...
Cold air damming setup will keep temperatures well below normal
through the early part of the next week. A gradual warming trend is
expected by the middle part of next week into the weekend. Shower
and thunderstorm chances stick around each day through next week,
with the best chances likely after Monday.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 145 PM EDT Saturday: The synoptic scale feature of interest
this weekend remains the uncommon summer CAD regime.  With the NE
sfc flow, lingering ovc conds and showers, Foothill and Piedmont
temperatures are struggling to climb into and/or thru the 70s this
afternoon. Thunderstorms along with a heavy rain possibility will be
limited to the wedge periphery which in our case is in the Smokies
where the 12z HREF progs 30% or greater chances of localized 3
inches of rainfall within this instability axis.  Elsewhere,
scattered showers will continue to generate within the
upglide/upslope flow above the sfc based stable layer.  As tonight
wears on, shower chances will linger regionwide within the Easterly
flow with sensible wx featuring ongoing considerable cloudiness and
patchy fog and drizzle.  Despite the lingering cool air wedge and NE
sfc flow on Sunday, impingement of drier air from the NNE will give
rise to increasing chances of brightening skies along and east of I-
77 but more a pessimistic sky and shower fcst exists the further
south one travels along the Appalachian chain. Showers should become
numerous again on Sunday acrs the SW cwfa and much of the mountains
and fthls will see 70s once again for maxes.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 100 PM EDT Saturday: In-situ CAD will be steadily locked
in over the area to start the forecast period as a surface high
located offshore the New England Coast continues to nose in from
the northeast. Dry surface layer and weak Atlantic Fetch atop the
surface will hold the CAD dome strong, especially with a LI between
4-6 per the SREF keeping high static stability in place. In this
case, CAD should stick around through the short-term period without
an obvious erosion mechanism. Model guidance have been persistent
over the past 24-36 hours of drier conditions for Monday as a
second surface high shifts over New England and Atlantic Canada
and reinforces the CAD dome and drier air at the surface. PoPs
only remain in the slight chance to chance range in this setup as
light on and off drizzle and showers still can`t be ruled out in
the presence of CAD. However, a slug of better deep layer moisture
will return Monday night into Tuesday as a digging shortwave trough
marches east from the central CONUS, toggling the flow above the
surface layer to a south-southwesterly component. As a result,
an uptick in PoPs is evident, especially by Tuesday with the
return of better moisture and isentropic lift. Instability will
be very low, but there is evidence of elevated instability, which
could result in heavier showers and isolated thunder during the
diurnal period Tuesday. PoPs ramp back up into the likely category,
especially in the southwest mountains and locations west of I-26,
where the better isentropic forcing is located.

The driest air will be present Sunday night and Monday, leading
dewpoints to drop into the upper 50s to lower 60s. In combination
with the cooler, drier subcloud layer and extensive cloud cover
settled in Sunday night, expect overnight values to end up 4-8
degrees below normal. Continued CAD conditions will keep afternoon
highs on Monday 10-15 degrees below normal. Slightly better moisture
transport will help to uptick dewpoints a few degrees by Monday
night to go along with continued cloud cover. Overnight lows will
run 3-6 degrees below normal as a result. With better WAA filtering
in above the CAD dome, helping to raise dewpoints, temperatures
are forecasted to uptick a few degrees and only run 8-12 degrees
below normal.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
As of 145 PM EDT Saturday: The aforementioned shortwave trough in
the short term is shown shifting over the Deep South and breaking
down as the feature gets mushed in between an anticyclone over
the southwestern CONUS and another over the western Atlantic
Wednesday and Thursday. In response, deep moisture will continue
to translate over the southeastern CONUS through a good portion
of the workweek. The middle part of the week will keep a weak
in-situ CAD in place, but the stalled boundary to the south will
have a surface low ride along it and potentially deepen offshore
the Carolina Coast once it taps into the Gulf Stream. In this case,
the CAD dome should begin to gradually erode by next Thursday and
Friday per the GFS and Canadian from the coastal low, leading
to better surface divergence. The ECMWF isn`t as excited about
the coastal low potential, but all of the deterministic filter in
a strong Atlantic Fetch in the presence of the stalled boundary
through much of the workweek. Expect higher PWAT values (~2.00")
and for the overall setup to be unsettled through a good portion of
the forecast period, with diurnal enhancement. Better solar heating
will likely erode any true CAD by the end of the workweek as only a
residual cold pool possibly holds steady. Temperatures for Wednesday
remain 5-10 degrees below normal, but a gradual warming trend is
evident through the rest of the forecast period, but values should
stay a few ticks or so below normal as elevated PoPs and cloud cover
hold steady with the presence of a weak residual cold pool.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Flight restrictions, mainly in the form of
IFR/MVFR cigs, remain present acrs much of the FA this afternoon
within the cool NE flow.  Scattered to numerous, but mainly light
showers, will continue to develop near all terminal locations into
this evening.  Numerical guidance is in decent agreement with
respect to an overall improvement in cigs by this evening, however
for time being, I am leery about latching onto this fast improvement
in conditions within the lingering CAD regime.  At any rate,
overall, still will be dealing with showers and cigs on Sunday as
the NE sfc winds continue, but the consensus is a return to
widespread VFR conditions tomorrow.

Outlook: Sct to numerous showers will be possible again on Sunday,
especially over the mtns and western SC Upstate. A return to more
typical summertime weather is expected early next week.

&&

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

&&

$$

SYNOPSIS...CAC
NEAR TERM...CSH
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...CSH