589
FXUS62 KGSP 211053
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
653 AM EDT Thu Aug 21 2025

.SYNOPSIS...
The chances for mainly afternoon and evening showers and
thunderstorms increase into the weekend.  Temperatures start
out near normal then fall below normal for the weekend. Cooler
and drier conditions develop early next week after a cold front
crosses our region.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 640 AM EDT Thursday...Starting out with a clean slate, but
plenty of evidence of abundant low level moisture on satellite
imagery. For today, now that Erin would be moving off well to our
east, we`re still under the same regime as yesterday. Not exactly a
defined upper low, but a baggy mid/upper trof overhead with weak and
confused flow in the profiles. There should be more than sufficient
low/mid moisture and a weak northeasterly upslope component this
afternoon to perhaps enhance the development of showers and storms
over the mountains. Precip probs are likely near the Escarpment
this afternoon, and once again, the flow will tend to drift them
more to the S and SW into the evening hours. That means that probs
taper off toward slight chance as you get farther east of I-77,
where the situation is less favorable with even weaker forcing. The
convective environment will be modest at best, with sfc-based CAPE
on the order of 1500 to 2500 J/kg N to S in the afternoon under
weak shear, suggesting a low threat of severe storms. The chances
of flash flooding are a bit greater because of some small potential
for storms to anchor near the Blue Ridge Escarpment. Temps should
be close to normal this afternoon, though it will feel more humid,
but not enough to cause heat index issues.

For tonight, the guidance develops a slightly better and more
easterly low level flow overnight, which the CAMs latch onto and
force precip across parts of the foothills and western Piedmont
of the Carolinas. There is slightly more concern for heavy rain
with slow moving storms late tonight as precipitable water will
remain high and warm cloud depth is thick. This may bear some
watching. Low temps will be near normal.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 1215 AM Thu: Sfc high will set up over the Mid-Atlantic coast
and support a net southeasterly flow up to about 850 mb, with N to NW
flow persisting higher aloft. Stalled boundary will effectively be to
our south. A weak circulation persists at 500 mb but it is
questionable whether that will have any effect on sensible weather.
Deep saturation seen on prog soundings; lapse rates are accordingly
poor, but very skinny elevated CAPE still develops even on the GFS
over much of the CWA. The high has the most limiting effect over the
NC I-77 corridor, with only low chances for precip there. Likely PoPs
result along the E/SE facing Escarpment, in the Savannah Valley and
western Upstate, with categorical values over the SW NC mountains
where moisture and upslope forcing are best.  Convection will be
limited in scope by the skinny CAPE, but locally heavy rain will be a
concern if/where a t-storm manages to develop.  Abundant cloud cover
and weak CAA will keep highs several degrees below normal, with
Escarpment areas remaining in the lower 70s if not a bit cooler.
Friday night, migration of the sfc high offshore will veer winds and
develop weak upglide over the front; MUCAPE falls off overnight. PoPs
diminish slowly but linger most of the night in our southern zones
under the best upglide.

Saturday, the SE`ly flow continues over the front and toward the
Escarpment and some degree of upglide will continue over the front,
so similar to Friday in those regards. Upper trough axis drifts east
and drying occurs above 500 mb, which will take away some of the
moisture in the column, and induces very subtle cooling aloft. Low
level temps are a bit warmer and capping is weaker or nonexistent,
and convection is a bit more likely. Altogether, PoPs trend higher in
our east with the effects of the high seemingly less of a factor;
similar likely to categorical values near and just south of the
higher terrain. Temps are still below normal but slightly warmer than
Friday. By Saturday night, heights being to fall ahead of the cold
front and trough axis moving out of the west. An inverted sfc trough
or developing low may form off the GA/SC coast as the upper trough
digs, but such development still appears of little to no consequence
for us. Southerly flow, deep moisture, and likely some lingering
MUCAPE implies a continuing chance for precip overnight over much of
the CWA, particularly the mountains.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 115 AM Thu: Cold front is progged to be near the NC/TN border
at 12z Sunday and should progress across the CWA thru the course of
the day. SBCAPE values from the LREF global model ensemble peak near
1000 J/kg ahead of the front, with 0-6km shear peaking around 20 kt.
20/12z ECMWF depicts what appears to be loosely organized convective
clusters, which makes sense given the shear/instability. DCAPE is
sufficient from the LREF that a few near-severe gusts could result,
but heavy rain is the more likely impact. Temps should be a bit
warmer than Saturday but still a little below normal. A few
showers/storms could linger into Sunday evening in our eastern zones,
but precip chances drop below slight-chance by midnight. Drying aloft
looks to result in deeper mixing Monday which should bring dewpoints
into the upper 50s or lower 60s during the afternoon. Downslope flow
will bring temps back to around normal east of the mountains; RH does
not look to reach critically low thresholds even using the 10th
percentile of NBM.

Cooler air settles in by Monday night with morning lows several below
normal Tue morning. Temperatures trend cooler Tue and Wed; highs Wed
look to be in the upper 70s across most of the Piedmont, with
early fall-like dewpoints in the lower to mid 50s.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: Satellite imagery/sfc obs show a patchy
MVFR/low VFR stratocu deck developing and moving southward across
the western Piedmont and NC foothills and over the middle of
the Upstate at issuance time, with more clouds to the north
moving in that direction. Expect that with minimal sfc heating
to act on abundant low level moisture, the MVFR bkn ceiling will
develop/expand by mid-morning. That should give us a decent chance
to have at least a temporary MVFR ceiling restriction at most
terminals. Wind will be light and favor a N to NE direction. The
CAMs are in good agreement with developing scattered/numerous
storms in the afternoon over the mtns/foothills of NC, which would
drift to the S and SW over the western Upstate. For that reason,
all terminals not named KCLT get a TEMPO with timing based on the
HRRR depiction, followed by a PROB30 into the late evening. The
threat for storms looks lower to the east, so KCLT will only get
a token PROB30 this evening. Some of the recent guidance manages
to bring some deep convection down from the north to reach KCLT
in the early morning hours, but confidence is too low to go any
higher or later with precip chances. Similar to this morning,
there will be a good potential for developing restrictions in a
moist easterly upslope flow by daybreak Friday.

Outlook: Shower and thunderstorm chances, as well as their
associated restrictions, linger through the weekend, with drier
conditions returning by early next week. Fog and low stratus may
develop overnight into the early morning hours each day.

&&

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

&&

$$

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