942
FXUS62 KGSP 190548
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
148 AM EDT Thu Jun 19 2025

.SYNOPSIS...
Hot and humid, with an increasing coverage of mainly
afternoon and early evening showers and storms on Thursday ahead of
a weak cold front. The front crosses the area Thursday night,
ushering in drier air and quieter weather for the first half of the
weekend.  By the latter half of this weekend, heat and humidity work
back into the area in full force with temperatures several degrees
above normal.

&&

.NEAR TERM /THROUGH TODAY/...
As of 130 AM EDT Thursday: Looks like the quietest night of the
string, with maybe an outside shot at a random shower over the
mountains near the TN border. A patch of higher level cloudiness
that has developed over the mtns may keep the valley fog/stratus at
bay through daybreak. Lows will be seasonally mild and above normal.

The shortwave will traverse the OH/TN Valleys during the day on
Thursday, allowing for the attendant cold front to inch closer to
the region. Pre-frontal convection is expected to develop ahead of
the front and should push from west to east across the CFWA during
peak heating. Deep layer shear (30-40 kts) supports the potential
for supercell/multicellular mode to going along with deep SBCAPE
(2000-3000 J/kg) and drier mid-levels leading to stronger DCAPE
(800-1000 J/kg). Any surges in the organized convection could make
for a more widespread damaging wind gusts. The Day 2 Slight risk
highlights the NC Piedmont, but CAMs show this potential across
the Upstate and northeast GA as well, so wouldn`t be surprised
if this gets expanded before the onset time of severe weather
potential Thursday afternoon. Drier conditions will filter in
behind the loosely organized convective line Thursday night,
while the main frontal zone should make a full fropa across the
CFWA early overnight Thursday. Lower dewpoints and dry advection
will lead to cooler overnight lows with values near-normal.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
As of 115 PM Wed: Trough axis will push gradually further off the
East Coast Friday and Friday night, with upper ridge building over
the Southeast states in its wake. Closed 500mb contour develops
during the day Saturday. The ensuing anticyclone is the story for
the weekend, deepening to about 597 DM by Sunday as it shifts over
the central Appalachians.

Following the cold front, dewpoints look to fall back several
degrees Friday, with afternoon values in the lower 60s in most
spots.  Temperatures won`t fall back quite as much with weak
downslope N to NW winds at 925-850mb and strong June sunshine
allowing maxes only a couple of degrees cooler in our north, and
at or slightly above Thursday`s values in the south. Modification
and rising thicknesses under the building ridge will result in
a warming trend Sat and Sun.  Most model guidance has trended
slightly lower with dewpoints those days; NBM now seems to reflect
an appropriate amount of afternoon mixing and think mixing MOS
or 10th percentile values is likely to be too low, so used the
straight NBM values. Heat index returns to the mid-upper 90s Sat
southeast of I-85, and to that level across most of the Piedmont
Sun (low 100s possible in some spots SE of I-85).

Daily QPF response has also trended downward in some of the
deterministic models and LREF probabilities of measurable precip
have also declined. Seeing some capping in prog soundings which was
not present before, but which would have made sense. Altogether,
these findings support PoPs remaining below slight-chance each day,
through Sunday night.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 215 PM Wed: Little large-scale change in the pattern for the
medium range. Weak southeasterly low to midlevel flow will continue
on the southern periphery of the upper anticyclone Monday into the
middle of next week. Temperatures continue a slow climb each day such
that max temps Mon and Tue afternoons are expected in the upper 90s
across a large swath of the Piedmont. Dewpoints are expected to trend
higher, with fewer ensemble members depicting as much of a diurnal
dip by early next week as airmass modification continues. Although
lapse rates unsurprisingly remain mediocre under the ridge, the
rebound in temps and dewpoints suggests increasing diurnal
instability and the return of diurnal showers/storms Mon and Tue,
with chances Tue back to about climatological (chance mtns/foothills,
slight-chance Piedmont). Heat index also looks to top out in the
100-105 range over most of the Piedmont Mon and Tue, approaching Heat
Advisory criteria.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: Prevailing VFR at all terminals outside of
thunderstorms this afternoon and evening, but some restrictions
possibly developing in the pre-dawn hours on Friday. A stronger
SW flow ahead of an approaching cold front will keep a steady
wind across the region once we mix out the morning inversion,
with frequent gusts through the afternoon and early evening. Low
clouds will generally remain scattered away from storms. Speaking
of which, scattered storms are expected to develop and move across
the region in the afternoon and evening, but the coverage and
timing details are unclear. The mesoscale model guidance shows
poor run-to-run continuity. Until we have an idea about how the
remnants of upstream convection behave this morning, we might not
be able to nail it down enough to go with a more targeted TEMPO
group at any of the terminals. The storms should come to an end
with a frontal passage in the late evening, after which winds will
veer to NW and become light.

Outlook: Drier conditions return behind a cold front Friday into
the weekend. Fog and/or low stratus will be possible each morning
over the mtns and near the rivers.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...CAC/CP/PM
SHORT TERM...Wimberley
LONG TERM...Wimberley
AVIATION...PM