368
FXUS62 KGSP 142205
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
605 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 to scattered showers and thunderstorms expected to linger
thru the late evening.

2) Another round of showers and thunderstorms is expected during the
afternoon and evening on Sunday.

2) Warm and humid east of the mountains.

As of 5:45 PM EDT Saturday: A handful of clusters of showers and
thunderstorms continue to gradually make their way eastward across
our fcst area early this evening. Over the past few hrs some of the
storms have become stronger, with one storm over Caldwell County,
NC prompting a warning. Otherwise, most of the convection is more
run-of-the-mill.

As for the bigger picture, our area becomes situated between 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 thunder-
storms to develop. The cloud cover plaguing the area earlier has con-
tinued to scatter out, allowing plentiful sunshine to reach the sfc.
Thru the evening and into the overnight hrs, 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 aftn. So rinse and repeat as the typical summertime
pattern emerges. Isolated and locally heavy precip possible with any
developing storm. Temperatures gradually warm into the upper 80s out-
side of the mtns.

&&

.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 230 PM EDT Saturday...

On Wednesday, the subtropical ridge should expand westward
briefly ahead of a mid-latitude trough propagating into the
upper Mississippi River Valley.  Guidance is in disagreement on
the timing and placement of this trough and is therefore not in
agreement about the dominance of the ridge.  Therefore, the NBM
splits the difference of the opposing influences, keeping high-end
likely/low-end categorical PoPs over the mountains and dropping PoPs
to chance across the central Piedmont.  It is possible PoPs will
trend lower still if the consensus builds on the ridge/trough timing
and placement, especially across the eastern zones.  Increasing
thickness and persistent SWly deep-layer flow support yet another
degree or two increase in high temperatures, with lower 90s expected
across the Piedmont.  There is a bit better support for afternoon
mixing, but the NBM is trending more humid per usual.  For now,
the forecast dewpoints are generally a few degrees lower than
NBM guidance on Wednesday in deference to the anticipated mixing.
Nevertheless, with higher temperatures compared to Tuesday, heat
index values are likely to still top out near 100 in the favored
Piedmont areas.

Guidance is coming into a bit better agreement that the trough
will approach the area on Thursday and that the trough axis will
cross the area on Friday.  This supports the ensemble mean of a
frontal passage sometime later Thursday or early Friday morning,
generally after peak heating.  Therefore, the front should
enhance forcing to support the decent instability in place across
the area, especially over the mountains for Thursday.  Also,
the overall pattern is supportive of an increase in bulk shear
into the 20-30 kt range, which suggests a bit better chance for
strong-to-severe thunderstorms.  Obviously, there is plenty of
time to build confidence on these details, as the amplitude of
the trough is currently a bit anomalous for this time of the year.
Similar to Wednesday, more mixing was introduced into the forecast,
but dewpoints are still progged to reach or top 70 in much of
the Piedmont.  With high temperatures similar to Wednesday, heat
indices remain elevated.

If the fropa is successful, Friday looks to be drier, with more
climatological PoPs currently forecast.  However, these PoPs are a
function of the National Blend and if consensus on the post-frontal
airmass builds, these will have to be lowered in future forecasts.
By next weekend, there is a decent signal high-amplitude ridging
will develop from the Southeast into the southern Plains, which
would act to shut down nearly all convection and reduce humidity.
Nevertheless, with highs in the lower 90s on Saturday the heat
will continue.

&&

.AVIATION /22Z 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/JPT
SHORT TERM...JMP
LONG TERM...JMP
AVIATION...CP/JPT