429
FXUS62 KGSP 150601
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
201 AM EDT Sun Jun 15 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 TODAY/...
As of 150 AM EDT Sunday: One patch of remnant light rain will
exit the NW Piedmont shortly, but more rain will move northeast
across the mtns thru daybreak. Additional shower activity seen over
northeast GA will move northeast over the Lakelands and western
Upstate through the pre-dawn hours, but is not expected to be as
vigorous as it was last night. Precip probs were changed to reflect
this thinking. Temps will remain seasonally warm thru daybreak.

Otherwise, the convectively active and humid pattern will continue
as a weak upper trof gradually lifts across our fcst area on Sunday
and weakens in the process. By the end of the near-term period late
Sunday/early Monday, the trof will have essentially dissipated some-
where over the Atlantic Coast. At the sfc, we will remain under
moist, SLY low-level flow thru the period that will keep our fcst
area in an unsettled pattern. Most of the near-term guidance tries
to develop a weak lee trof over our CWA Sunday aftn/evening, but it
likely won`t have much impact on our sensible wx. Like the past few
days, we can expect sct showers and thunderstorms in the aftn and
evening. The severe potential looks minimal, but we may see some
stronger storms and possibly a few severe storms as well. For what
it`s worth, SPC does have our NE zones in a Marginal Risk area for
tomorrow, with damaging wind gusts and large hail being the primary
threats. In addition, WPC has our northern tier of zones under a
Slight Risk for excessive rainfall thru Monday morning. This is
somewhat con- cerning as this area has already received a fair
amount of precip this evening from training convection which has
resulted in some minor localized flooding. If they get more precip
tomorrow, more serious flooding could occur. Overall, much like the
past few days, the main threat across our area thru the period will
be the potential for additional localized flooding. Otherwise,
temperatures on Sunday will be similar to the past few days,
with highs near-normal.

&&

.SHORT TERM /TONIGHT 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 /06Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: The air mass across the region remains
warm and humid, thus a low cloud ceiling restriction could develop
just about anywhere at any time. That leaves us with a complicated
situation with variable restrictions at all terminals thru daybreak
or so. It seems likely that all terminals will be IFR or MVFR
at some point, but also have periods of VFR. KHKY has the best
chance for LIFR or lower thru daybreak. Either way, an MVFR ceiling
will pop up quickly with minimal heating by mid-morning and then
persist to midday, by which time the lowest clouds will scatter
out and lift above 030. Scattered thunderstorms are expected in
the afternoon and lingering into the early evening. Confidence is
best at KCLT in the mid/late afternoon. Looks more like a typical
summer day, with convective debris lingering into late evening,
then quieting down for the overnight.

Outlook: Showers and thunderstorms are expected each day thru early
next week. Late night and early morning fog and low stratus restric-
tions will be possible each day.

&&

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

&&

$$

SYNOPSIS...JMP
NEAR TERM...JPT/PM
SHORT TERM...JMP
LONG TERM...JMP
AVIATION...PM