241
FXUS62 KGSP 041031
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
631 AM EDT Mon Aug 4 2025

.SYNOPSIS...
Cold air damming lingers through the workweek before a coastal low
erodes the wedge this weekend. Below normal high temperatures can be
expected each afternoon through at least Saturday despite a gradual
warming trend Wednesday into the weekend. Shower and thunderstorm
chances stick around this week, with the potential for locally heavy
rainfall each day.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 630 am EDT Monday: Remnant cold pool/in-situ cold air damming
lingers across the region early this morning, and is likely to
remain more or less in place through the period, due largely to
lingering low cloud cover and eventually, precipitation, as multiple
rounds of (mostly) light-to-moderate rain are expected through
tonight. This will occur due to height falls to our west, which will
carve out a trough across the TN Valley and Deep South by the end of
the day. This will set up deep SW flow above the lingering stable
layer over our area, with PWATs forecast to increase to around 2" by
tonight as deep Gulf moisture advects into the area. Increasing
cyclonic flow aloft interacting with the deep moisture and
increasing isentropic lift will result in increasing precip chances
through the morning, especially across western areas, where PoPs
increase to 60-80% across the southwest quarter throughout the day.
Forcing increases further tonight, with isentropic and upslope lift
strengthening in response to accelerating flow aloft. Additionally,
chances will increase for remnant areas of convection streaming NE
from the unstable air along the Gulf Coast to move into the CWA.
Thus, PoPs increase to 60-80% across almost the entire CWA at some
point tonight. In light of the very moist environs and deep warm
cloud depths, the potential for locally heavy rainfall will increase
across western areas tonight, although a continued absence of
notable instability will limit the potential for extreme rainfall
rates. Max temps will remain around 10-15 degrees below climo, with
mins tonight about a category below normal.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 100 AM EDT Monday...

Key Messages:

1) Cold Air Damming Lingers Keeping Highs Each Afternoon Well Below
Normal

2) NBM Trending Cooler on Tuesday

3) Better Coverage of Rain Expected with the Locally Heavy Rainfall
Threat Ramping Up

With the southwestern periphery of a sfc high continuing to nose
down into the southern Appalachians, cold air damming will remain
locked into place through the short term keeping cool and dreary
conditions around. The latest run of the NBM is now trending 3-5
degrees cooler for highs on Tuesday allowing afternoon temps to run
~10-15 degrees below normal. Highs on Wednesday should end up ~2-6
degrees warmer compared to Tuesday but will still end up ~5-10
degrees below normal. Lows each night east of the mountains will
range from a few degrees below normal to normal, with lows across
the mountains ranging from near normal to a few degrees above
normal.

Mostly cloudy skies and overall better coverage of rain is expected
throughout the short term as upper shortwaves lift northeastward
across the forecast area. The NBM has likely to categorical PoPs
(60% to 80%) for most locations through the period with the
exception of areas along/near I-77. Lower PoPs are in place along
the I-77 corridor, ranging from high-end chance to low end likely
(45% to 60%). Did opt to go lower than the NBM regarding thunder
chances through the period due to CAD limiting sfc instability. The
00Z NAM keeps the highest SBCAPE and MUCAPE values mostly south and
east of the forecast area on Tuesday but it does continue to show
the potential for some instability to develop across the SW NC
mountains and across the far SE fringe of the forecast area during
peak heating. However, with the NBM trending cooler on Tuesday and
with mostly cloudy skies in place, confidence on any embedded
thunder developing is low. Embedded thunder chances appear to
increase on Wednesday, mainly across the NC mountains, NE GA, and
western SC Upstate (outside the heart of the wedge) as the 00Z NAM
shows instability developing across these zones. With warmer temps
expected during peak heating Wednesday, this looks plausible. With
PWATs ranging from 1.5" to 2.0" through the period, locally heavy
rainfall may lead to isolated flash flooding, especially considering
we already have fairly wet antecedent conditions in place.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 100 AM EDT Monday...

Key Messages:

1) Cold Air Damming Lingers through the Workweek Before a Coastal
Low Erodes the Wedge this Weekend

2) Despite the Gradual Warming Trend, Highs Remain Below Normal Most
of the Period

3) Locally Heavy Rainfall Threat Lingers through the Weekend
with Shower and Thunderstorm Chances Sticking Around

Cold air damming looks to hold on through at least Friday before
gradually eroding this weekend as a coastal low develops and drifts
towards the Carolinas. Now that all model guidance sources are on
board with the coastal low developing, confidence is higher on the
erosion of the wedge over the weekend. The latest GFS is now more in
line with the ECMWF, depicting wetter conditions through the long
term compared to this time yesterday. Thus, shower and thunderstorm
chances will linger through the remainder of the workweek and into
the weekend. NBM currently has the highest PoPs in place across the
mountain zones each day with lower PoPs elsewhere. PWATs will range
from 1.25" to 1.9" Thursday into Friday, increasing to 1.5" to 2.3"
over the weekend as the coastal low approaches. Both wet antecedent
conditions and elevated PWATs will act to keep the locally heavy
rainfall/isolated flash flood threat around throughout the long
term. Highs each afternoon will remain a few to several degrees
below normal through Saturday, becoming near normal to just below
normal on Sunday. Lows each night will end up near normal to a few
degrees above normal.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: An area of sprinkles and -DZ w/ increasing
coverage of embedded -RA could briefly reduce visby at the
upstate SC terminals early this morning...warranting tempos
for such. Otherwise, MVFR cigs are expected to persist at KAVL
and KAND through the day, while VFR conditions are expected
to prevail at the other sites until later this afternoon or
even this evening. The shower potential will steadily increase
through the day, especially across the western part of the area,
with Prob30s for -SHRA and MVFR visby conditions advertised at
all sites beginning at some point this afternoon/evening. Some of
these will probably need to be converted to tempos as confidence in
timing increases. Shower ramp up enough this evening to introduce
prevailing -SHRA along with lowering cigs. MVFR is expected at
most sites by midnight...extending to KHKY and KCLT by daybreak
Tuesday...when sites farther west should be deteriorating to
IFR. Winds will generally remain NE at 5-10 kts through the period.

Outlook: Precip chances remain elevated into Tue. Although
temperatures only gradually warm back up over the remainder of the
week, precipitation chances trend toward a more typical summertime
regime by Wed with chances mainly in the afternoons and early
evenings. Periodic restrictions remain possible thru late week,
especially overnight and in the morning.

&&

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

&&

$$

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