099
FXUS62 KGSP 170555
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
155 AM EDT Tue Jun 17 2025

.SYNOPSIS...
Hot and humid with daily chances for showers and thunderstorms
through Thursday. A cold front pushes across the area early
Friday, bringing a reduction in rain chances lasting through the
weekend. Although humidity looks lower this weekend, temperatures
will trend hotter.

&&

.NEAR TERM /THROUGH TODAY/...
As of 145 AM EDT Tuesday...Coverage and intensity of showers
and storms over the western Piedmont of NC continues to diminish
at this hour. Fortunately, rain rates are trending downward as
well, and the activity was moving along at a decent clip.
Rainfall amounts have been patchy by nature, but enough in some
places to push some streams up close to bankfull. Areas east of
US 321 are being watched for possible Flood Advisories.
Elsewhere...patches of remnant light rain moving up from
northeast Georgia will gradually rain out over the Savannah
River basin. After the activity ends completely, expect another
smattering of patchy dense fog or low stratus through daybreak.
Temps are going to remain above normal, with a very humid air
mass.

Otherwise...lows tonight will only drop into the 60s and 70s
making for another muggy night. Low stratus and patchy fog may
develop again overnight into daybreak Tuesday (especially for any
locations that receive heavy rainfall) but should lift quickly
after sunrise. Another day of diurnal convection can be expected on
Tuesday with the severe threat remaining low but with the locally
heavy rainfall/isolated flash flooding threat continuing.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
As of midday Mon, key messages:

1. Conditions will be somewhat less favorable for diurnal showers and
thunderstorms Wednesday compared to the previous day, so
chances/coverage should trend downward.

2. Approach of an upper trough and cold front imply coverage will
tick upward again Thursday, especially over the NC mountains.

3. Temperatures remain slightly above normal both days with typical
June humidity.

A compact shortwave trough is progged to be centered west of the
southern Appalachians Tuesday evening, primarily over central KY/TN.
Although model consensus is for it to fill and/or track northeastward
from there overnight, enhanced SW`ly flow will continue into our NC
mountains and some showers/storms could regenerate; PoPs persist most
of the night. A weak convergence axis associated with the trough does
appear to shift over the mountains during the day Wed.  Despite
similar CAPE and lapse rates, the mid to upper levels are subtly
drier and thus less conducive to deep updrafts.  The convergence axis
seems to help overcome that over the mountains, but not for the
Piedmont. While PoPs overall trend downward, they remain in likely
range over the mountains, and slight-chance to low chance most other
areas. Where storms do form, some training cannot be ruled out, so a
localized flash flood threat will persist, although decreased PWATs
will mitigate rates. Drier air aloft may increase storms` damaging
wind potential. With shear is likely to fall in the 20-25 kt range
over much of the area so multicell storms would be favored over pulse
storms, but damaging wind can`t be ruled out. No SPC risk contour in
our area as of this writing.

Sfc low will track thru the eastern Great Lakes region late Wed night
into Thu morning. Associated cold front and synoptic trough axis will
move across the Cumberland Plateau Thu, reaching the TN/NC border Thu
evening. Prefrontal convergence potentially will enhance convective
coverage compared to Wed, so PoPs are higher and persist longer into
Thu evening. Shear will improve a little bit in the faster midlevel
flow around the trough, with the mean closer to 25 kt in our north
and some ensemble members showing 30+ kt. The SPC Day 4 outlook,
issued overnight Sun night, depicts a 15% risk area centered in the
Mid-Atlantic, extending into the NC Piedmont ahead of the shortwave,
reflecting the slightly better shear but arguably moreso the
increased coverage. Damaging wind still would appear the most likely
threat. PWATs do increase again, but with storms moving a little
faster the threat of heavy rain probably will remain isolated.
Antecedent soil conditions will have had more time to deteriorate
where heavy rain repeats from day to day.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 200 PM Mon, key messages:

1. In the wake of a cold front, atmospheric moisture is likely to
decrease Friday, but probably will build back gradually over the
weekend.  Convective coverage likely will be reduced in this period
compared to in the middle of the week.

2. Temperatures will trend warmer Saturday and Sunday, potentially 6-8
degrees above normal by Sunday. Despite relatively low humidity, heat
impacts are possible in some areas.

Drier air looks increasingly likely to have sensible weather effects
in our CWA by Friday, following the cold fropa. The major
deterministic models and Euro/NAEFS ensembles suggest PWATs fall
below climo. In terms of dewpoint, most guidance members depict
values a few degrees lower Friday than in the midweek period, and
there is more spread among members on the low side of the mean,
suggesting some potential for a midafternoon dip via mixing.
Although that accordingly suggests lower CAPE, there appears
insufficient subsidence to produce a capping inversion, so a 20-30%
PoP is still warranted for most of the area. Upper anticyclone does
center over the area Saturday and linger Sunday, so the potential for
capping would appear higher those days, although surface moisture
does begin to build back as airmass modifies. Similar 20-30% PoP
distribution continues thru the weekend.

Friday will be slightly cooler over parts of the area via the fresh
post-frontal airmass, but trend warmer Saturday and Sunday via the
modification and light southerly flow. Aftn maxes will reach the
mid-90s over most of the Piedmont by Sunday, with the Little TN and
French Broad valleys flirting with 90 both days. Dewpoints will be
manageable and largely in the upper 60s across the Piedmont, but
areas southeast of I-85 are likely to have heat index above 100
Sunday, if not Saturday, in some cases the first period of heat
concern this year.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: The last of the storms appear to have moved
east of KCLT and KHKY, so the rest of the night should be just
a frustrating chase of patchy and variable low stratus and fog
that could affect any terminal from VLIFR to VFR. Terminals that
had rain are most likely to see restrictions, mainly the ones in
NC. The fog and low stratus should break up an hour or two after
sunrise if they form. Thereafter, looks like a typical hot and
humid summer day, with a brief MVFR ceiling possible in mid/late
morning, then a chance of thunderstorms in the afternoon and early
evening. Will opt for PROB30s as coverage looks scattered in the
model guidance and confidence is too low for TEMPOs. Once the
convection ends in the mid/late evening, more convective debris
clouds can be expected. Wind will generally remain SW thru the
period, but variable and gusty near storms.

Outlook: Isolated to scattered showers and thunderstorms are
expected each afternoon/evening through Thursday. Drier conditions
return behind a cold front Friday into Saturday. Fog and/or low
stratus will be possible each morning.

&&

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

&&

$$

SYNOPSIS...Wimberley
NEAR TERM...AR/ARK/PM
SHORT TERM...Wimberley
LONG TERM...Wimberley
AVIATION...PM