636
FXUS62 KGSP 141902
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
302 PM EDT Sat Jun 14 2025

.SYNOPSIS...
Seasonably warm and humid weather, with numerous showers and storms
each afternoon and evening, can be expected through Sunday. A
warming trend will begin on Monday, and daily showers and storms
will continue through most of the week.

&&

.NEAR TERM /THROUGH SUNDAY/...
Key Messages:

1) Isolated showers and thunderstorms possible late this evening

2) Warm and humid east of the mountains

3) Showers and thunderstorms during the afternoon and evening on
Sunday

As of 145 PM EDT Saturday: The CWA becomes caught in the middle of
two areas of high pressure, one over the southwest CONUS and the
other off the east coast. Meanwhile, the western edge of the Bermuda
high allows for a broad warm sector with an abundance of advected
moisture from the south, keeping the area locked into an unsettled
pattern. Synoptic forcing remains weak, but given the increased
PWATs and instability, should be more than enough to enact showers
and thunderstorms once again. The cloud cover plaguing the area
earlier have continued to scatter out, allowing plentiful sunshine
to reach the surface. Guidance from the CAMs suggest convection
minimal convection this afternoon. Though at this time of year, it`s
not uncommon for unreliable CAMs during more diurnally driven
convection. So cannot rule out a pop-up storm over the mountains
during peak heating. Through the evening and into the overnight
hours, shower and thunderstorm chances increase, mainly over the
mountains, as a shortwave passes above from the decaying upper low.
By Sunday, PoP chances increase again during the afternoon. So rinse
and repeat as the typical summertime pattern emerges. Isolated and
locally heavy rainfall possible with any developing storm.
Temperatures gradually warm into the upper 80s outside the mountains.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 230 PM EDT Saturday...

If we are sounding like a broken record, it`s warranted as the
overall pattern and expectations to start the work week remain
similar to previous forecast packages.  On Monday, westerly upper
level flow will begin to back west-southwesterly ahead of the next
shortwave trough.  Its proximity supports the continued trend
of categorical PoPs over the mountains with likely PoPs east,
given ample SBCAPE and weak but continuous moisture flux from
the central Gulf of America.  Poor lapse-rates and westerly bulk
shear values in the teens are not supportive of a notable severe
storm threat, though an isolated damaging microburst cannot be
ruled out, especially over the Piedmont, where forecast profiles
suggest a bit of dry air aloft/DCAPE.  However, over the Piedmont,
the potential for higher mixing heights and some warmer air just
above the mixed layer may work to inhibit convection at least
until later in the afternoon/early evening.  Profiles over the
mountains are expected to be fairly moist through the column
so there will be less of a strong storm threat there.  However,
with PWs at least near the 90th percentile area wide, and Corfidi
vectors suggesting a favorable environment for slow-moving/training
cells, heavy rain is likely for a few locations and an isolated
flash-flood threat will persist wherever convection does develop.
Expect high temperatures to tick up a degree or two from Sunday,
with dewpoints in the upper 60s to lower 70s during peak heating
over the Piedmont and mountain valleys continuing the trend of
uncomfortable humidities.

The upper-level shortwave is going to struggle to propagate
east into our area, as the subtropical ridge over the western
Sargasso Sea strengthens and builds west into the Southeast.
The strength of the ridge will deamplify the shortwave and cause
it to lift towards the central Appalachians later Tuesday, with a
weak trough axis draped on our western doorstep.  Therefore, there
isn`t much change in our PoP forecast from Monday, and with similar
profiles in place, not much change in the overall threats either.
Given the continued WSW to SWly deep-layer flow and a slight
increase in thicknesses, especially in the eastern zones closer
the ridge, expect high temperatures to increase a degree or two yet
again Tuesday afternoon.  If dewpoints do not mix out appreciably
(and we are not expecting them to), heat index values of 100-102
are possible over the Charlotte metro and central Savannah River
Valley region.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 256 AM EDT Saturday...

Unsettled weather will continue for much of the extended
forecast period. Through at least Thursday, there`ll be little
change in the synoptic pattern...which is to say subtropical
ridging will remain in place and low-level moisture flux will
continue, if perhaps weakening Wednesday and beyond as the
Bermuda High expands westward and forces low-level winds to
become more westerly. Expect diurnal showers and thunderstorms,
with low-end severe risk...but at least some concern for hydro
issues...through Wednesday.

Wednesday night, a z500 trough will eject out of the northern
Great Plains, quickly crossing the Midwest and entering the
Ohio Valley on Thursday.  Operational guidance is in marginally
better agreement than earlier forecasts on the surface front`s
arrival in the Carolinas late Thursday evening or overnight...but
long-range ensemble solutions still depict significant variance in
timing...with some solutions bringing the front in early enough
Thursday for an elevated convective risk and others bringing it
in as late as the diurnal minimum Friday morning.

In any case, the front will bring in some slightly drier air, but
won`t be strong enough to really dislodge the Bermuda High...which
guidance depicts maintaining its strength if perhaps retreating
eastward a bit.  At best, it appears all we can expect is a lull
in afternoon showers for a day or so...and little if any relief
from unseasonably warm temperatures, which by the end of the period
may climb into the low- to mid-90s.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Starting  off the TAF period with a mix
of VFR/MVFR conditions as lower stratus continues to clear out.
Confidence is low on the amount of TSRA this afternoon, hence a
PROB30 at all sites through this evening. There is a possibility for
some additional TSRA before midnight at a few locations. Will keep
VCTS for now. By daybreak, the amount of moisture in the area could
bring vsby/cigs down into the MVFR/IFR, especially at KAVL, before
12z. It doesn`t look as widespread as previous days, but lower
stratus is still possible briefly for most sites affecting cigs.
Slow improvements during the morning hours as the lower cloud deck
clears out once again. Then, rinse and repeat as another round of
pop-up TSRA is expected across all sites Sunday afternoon. Winds are
expected to remain S/SW and relatively light.

Outlook: Showers and thunderstorms are expected each day through
early next week. Late night and early morning fog and low stratus
restrictions each day.

&&

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

&&

$$

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