158
FXUS62 KGSP 030557
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
157 AM EDT Sun Aug 3 2025

.SYNOPSIS...
Cold air damming keeps shower and thunderstorm chances as well as
below normal high temperatures around the rest of this weekend and
into much of next week. Despite below normal high temperatures, a
gradual warming trend can be expected through next weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 140 am EDT Sunday: Summer cold air damming regime continues
across the forecast area this morning. With the parent high located
relatively far to the south across the northern Mid-Atlantic,
relatively deep NE flow has pushed drier air into the eastern zones
this morning, lifting the cloud layers and generally bringing
an end to -DZ and showers. Meanwhile, showers continue across
western areas within deeper moisture plume that is aligned with
upslope flow and weak isentropic lift. Some of this activity may
become more shunted to the SW as drier air continues to gradually
filter through the CWA. Nevertheless, instability west of the CWA
interacting with thermal moisture boundary delineating the leading
edge of the CAD should result in shower development later today,
some of which will wander into western zones. Upslope flow will
also continue to some degree, so 50-60 PoPs are warranted across
roughly the western 1/3 of the CWA from late morning through
the afternoon. Precip chances taper down to less than 20% in
the drier air east of I-77. Instability in our forecast area
is expected to be limited to the Smokies and vicinity, and a
thunder mention is therefore confined to that area. Temps will be
warmer than yesterday, especially across the NC Piedmont, where
lower 80s expected with at least some peaks of sun likely this
afternoon. Still...maxes will be around 10 degrees below normal
give or take. The unseasonably cool conditions continue into tonight
with showers continuing, albeit becoming more spotty in coverage.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 100 AM EDT Sunday...

Key Messages:

1) Cold Air Damming Remains in Place

2) Well Below Normal High Temperatures Continue

3) Shower and Thunderstorm Chances Ramp Up through the Period

Cold air damming remains in place early next week thanks to the
southern periphery of a sfc high nosing down into the southern
Appalachians. Despite the NBM trending slightly warmer regarding
afternoon temps for some locations during the short term, highs each
afternoon will still end up around 5-10 degrees below normal. Lows
each night will end up a few degrees below normal to near normal.
Mostly cloudy skies will continue, although some sunshine may peak
through across mainly the NC Foothills and Piedmont Monday morning
into Monday afternoon before cloud cover increases again across
these zones by Monday evening.

The 00Z HRRR and NAMNest, as well as most of the global guidance
sources, show rain chances steadily increasing from SW to NE
throughout the day Monday. However, NBM PoPs on Monday appear to be
more in line with the GFS which continues to be the driest of the
guidance sources. The NBM only has chance PoPs across much of the
forecast area and this could be too low per the high-res guidance as
well as the ECMWF, NAM, and Canadian. Thus, confidence on Monday`s
PoPs on remains low. Outside of the mostly dry GFS, guidance
generally agrees that coverage of rain will continue increasing
Monday evening into Tuesday night. The NBM PoP trend does reflect
this trend so confidence on PoPs the remainder of the short term is
higher. Majority of model guidance, with the exception of the NAM,
has very little in the way of SBCAPE and even MUCAPE early next
week. However, the NAM is showing SBCAPE and MUCAPE values from
~1,000-1,500 J/kg across the far SE fringe of the CWA Tuesday
afternoon and evening. Thus, a few thunderstorms look plausible,
especially during peak heating on Tuesday. However, confidence is
low with only the NAM depicting destabilization. PWATs will steadily
increase from south to north throughout the short term so localized
hydro concerns may return, especially on Tuesday.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 100 AM EDT Sunday...

Key Messages:

1) Cold Air Damming May Linger through Entire Period

2) Gradual Warming Trend is expected but Highs Remain Below Normal

3) Shower and Thunderstorm Chances May Stick Around

With the southwestern periphery of the sfc high extending down into
the southern Appalachians throughout the long term, and with no real
mechanism to erode the wedge (at least per the NBM and ECMWF),
persistent NE sfc winds may help keep cold air damming locked into
place, albeit weaker as time goes on. However, both the GFS and
Canadian depict a coastal low developing, which could help erode the
CAD layer either partially or completely. Confidence on CAD erosion
is very low with the GFS showing an impressively strong coastal low
developing the second half of the period while the Canadian develops
a much weaker coastal low. The ECMWF does not even have a coastal
low developing...which is more in line with the NBM in keeping the
CAD layer around. The GFS remains the outlier with mostly dry
conditions while the Canadian and ECMWF depict wetter conditions
through much of next week across the western Carolinas and northeast
Georgia. All this to say, confidence on the sensible weather will be
very low during the second half of the forecast period due to the
inconsistency from the global models regarding the overall weather
pattern. PWATs may remain elevated, especially if the wetter model
solutions pan out, so localized hydro concerns could linger through
the long term. Although temps will be on a gradual warming trend,
highs appear to remain a few to several degrees below normal each
day, with lows each night roughly around normal (per the NBM).
However, if the wedge erodes the second half of the period, temps
could end up much warmer (again confidence is low). Per the NBM,
mostly cloudy skies linger through Thursday evening, possibly
breaking up a bit overnight Thursday into Friday morning before
increasing again Friday afternoon and evening. The same pattern
regrading cloud cover repeats itself overnight Friday into Saturday.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: NE surface winds of 5-10 kts continue
across the Terminal Forecast Area early this morning. The NE
winds are pushing drier near-surface air into the area, which
has resulted in KCLT improving to VFR (KCLT should remain VFR
through the period). Meanwhile, IFR conditions persist across most
of the remainder of the area, but steady improvement to MVFR is
expected in most areas by around daybreak, with VFR expected at all
sites except perhaps KAND by late morning as the depth of drier
air steadily increases. Meanwhile, showers and areas of -DZ will
continue across western areas through at least daybreak...resulting
in periods of 2-6SM at all sites except KCLT. Shower chances are
expected to increase a bit this afternoon, with Prob30s for -SHRA
advertised at all sites. Winds will remain NE at 5-10 kts through
at least the afternoon...weakening a bit this evening.

Outlook: Relatively cool and damp conditions are expected Monday,
with better chances for showers. Although temperatures only
gradually warm back up over the remainder of the week, precipitation
chances trend toward a more typical summertime regime with chances
mainly in the afternoons and early evenings by midweek. Periodic
restrictions remain possible.

&&

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

&&

$$

SYNOPSIS...AR
NEAR TERM...JDL
SHORT TERM...AR
LONG TERM...AR
AVIATION...JDL