357
FXUS62 KGSP 141751
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
151 PM EDT Wed Aug 14 2024

.SYNOPSIS...
Dry high pressure gradually builds in from the north through
Thursday, resulting in mainly isolated afternoon showers and
thunderstorms in the mountains. The high will drift east off the
East Coast Friday, as a cold front approaches from the west over
the weekend. The front will bring a return of better chances of
shower and thunderstorms through Sunday, then lower chances early
next week with temperatures near normal.

&&

.NEAR TERM /THROUGH TONIGHT/...

Key Messages...

1) Below Normal Temperatures for Most Locations This Afternoon
Despite More Sunshine than yesterday

2) A few showers Possible Across the Mountains this Afternoon and
Early Evening with Dry Conditions Expected Elsewhere

As of 140 PM EDT Wednesday: A quiet afternoon thus far. Vis
satellite imgery shows some enhanced cu on the ridgetops, so expect
a few showers to develop over the next hour. Mesoanalysis shows up
to 500 J/kg of CAPE underneath a subsidence inversion, so isolated
showers looks like it would still be a decent bet. Temp/dewpoint
trends still look good, so no big changes.

Otherwise...it will be sunnier afternoon compared to yesterday,
but highs across the forecast area expected to be 3-5 degrees below
climo, east of the mtns at least. Slightly warmer temps are expected
across the eastern half of the forecast area this afternoon,
with the western zones seeing slightly cooler temps. The 15Z HRRR
continues to show some low-topped shower activity this afternoon
that eventually gets pushed southward over the western Upstate
early this evening. Thus, we will keep a slight chance PoP in place
across some of the western zones during this timeframe. With the
HREF ensemble probability showing SBCAPE not exceeding 500 J/kg
during peak heating, mostly showers are expected. Dry conditions
can be expected tonight with the potential for another round of
mountain valley fog and low stratus. Some fog may spill into the NC
Foothills again but confidence on this is low for now. Lows tonight
will remain a few degrees above climo across the western zones
with low near climo to just below climo across the eastern zones.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 230 AM EDT Wednesday: Flat Upper ridging will build into the
area Thursday into Friday from the Lower MS Valley, while a deep
trough digs into the Upper Midwest. The trough will continue to dig
into the Ohio Valley Friday into Fri night with the upper ridge axis
shifting east off the East Coast. Meanwhile, a sfc ridge axis will
be along the spine of the Appalachians at 12z Thursday, and shifts
to the East Coast by 12z Friday, which will begin a weak return flow
atop the forecast area. An area of low pressure will track across
the Great Lakes, bringing a trailing cold front into the Ohio Valley
on Friday. A moderately unstable warm sector air mass with some bulk
shear upstream of the NC mountains may support organized convection,
but confidence is low on surviving all the way to the mountains. But
the mountains should see an uptick in convective activity with
diurnal heating and a SWLY upslope flow. Less instability (and
possibly some CIN) should keep the Piedmont largely quiet Friday.
Temps will be a degree or two below normal Thursday and warm to near
or slightly above normal Friday.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 245 AM EDT Wednesday: The main concern will be PoPs and any
severe potential with a cold frontal passage on Saturday. A digging
upper trough should provide DPVA for synoptic support, while SWLY
low-level flow should bring in some moisture along/ahead of the
front. The frontal forcing doesn`t look that strong, however. So
not a slam dunk for severe storms, but probably will be at least
a marginal threat. The 00z guidance has come into better agreement
on the trough axis pivoting east to the Eastern Seaboard, allowing
the front to reach the Carolina Coast Sunday into Monday. Drier
air will filter in from the NW atop the forecast area and should
cut back on diurnal convective chances for the first part of next
week. Temps will be slightly above normal Saturday, then cool to
near normal behind the front.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
At KCLT and elsewhere: VFR across the Upstate and wrn Piedmont
through the period, with mostly a light/variable wind. Won`t rule
out a brief bkn ceiling around 040 through sunset. Wind should
come back up from the SW to SE after sunrise. Fog/low stratus will
be a problem at KAVL/KHKY late tonight. The guidance develops the
MVFR then IFR restrictions at both sites after midnight, and this
seems reasonable given the fair conditions. Both terminals should
see a dropoff to IFR as fog develops off the rivers, with LIFR
or VLIFR at least temporarily possible. The improvement might not
take place until 13Z-14Z Thursday.

Outlook: Isolated diurnal convection returns Thursday. Coverage of
convection increases Friday into Saturday as a cold front approaches
out of the west. Patchy fog and low stratus will be possible each
morning in the mountain valleys and in any locations that received
heavy rainfall the day prior.

&&

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

&&

$$

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