767
FXUS62 KGSP 141020
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
620 AM 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.

&&

.NEAR TERM /THROUGH TONIGHT/...

Key Messages...

1) Patchy to Dense Fog at Times Expected Across Portions of Western
North Carolina this Morning

2) Below Normal Temperatures for Most Locations Today Despite More
Sunshine

3) Isolated to Scattered Convection Possible Across the Mountains
this Afternoon and Early Evening with Dry Conditions Expected
Elsewhere

As of 620 AM EDT Wednesday: Patchy fog and low stratus has developed
this morning across portions of western North Carolina. Locally
dense fog has developed across the northern NC Foothills with
Hickory and Morganton both reporting dense fog. Thus, went ahead and
issued an SPS through 9am for patchy to locally dense fog for
locations along and north of I-40. Fog and low stratus should mix
out by mid-morning. Otherwise, cloud cover will continue to
gradually decrease through this morning. Temps are near to just
below climo along/near I-77 and I-40, with temps running a few
degrees above climo elsewhere. Dry conditions will persist area-wide
through at least this morning.

It will be sunnier today but highs across the forecast area expected
to be near climo to a few degrees below climo. Slightly warmer temps
are expected across the eastern half of the forecast area this
afternoon, with the western zones seeing slightly cooler temps. 00Z
CAMs show scattered convection developing this afternoon and early
evening across the mountains, with dry conditions elsewhere. Thus,
have chance PoPs in place across 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.
However, an isolated thunderstorm cannot be entirely ruled out,
mainly along the southern Blue Ridge Escarpment. 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 /12Z WEDNESDAY THROUGH SUNDAY/...

Key Messages...

1) Patchy to Dense Fog at Times and Low Stratus are the Main
Concerns through Daybreak at KHKY and KAVL this Morning and Possible
Again Tomorrow Morning

2) Scattered Showers will Develop at KAVL this Afternoon with Dry
Conditions Lingering Elsewhere

3) Mostly MVFR to VFR Cigs Expected through the 12Z TAF Period

At KCLT and elsewhere: Dry conditions will continue through this
morning. Patchy to dense fog and low stratus have already developed
at KHKY, with only low stratus at KAVL so far. Have TEMPOs at both
sites to account for the fog/low cigs.  Went ahead and added TEMPOs
for MVFR cigs at both KGSP and KGMU for this morning per the latest
OBS and satellite imagery. Fog/stratus should mix out around 13Z-
14Z. Still seeing mostly MVFR to VFR cigs elsewhere this morning
with mostly calm to light N/NE`ly across the terminals. Winds east
of the mountains will remain NE through the morning hours before
gradually turning more ENE/E this afternoon. Winds will then briefly
toggle back NE this evening into late tonight. Winds at KAVL should
gradually turn N/NE after daybreak. KAVL will then see winds turn
SE`ly this afternoon into this evening before going calm to light
and VRB tonight. Have a TEMPO for -SHRA at KAVL this afternoon as
showers are expected to develop across the mountains. Dry conditions
will persist elsewhere. Mountain valley fog and low stratus may
develop tonight into daybreak Thursday, with KHKY looking to have a
lower fog potential compared to this morning. Dry conditions are
expected tonight into Thursday morning. Winds should gradually turn
SE`ly across the terminals Thursday morning after sunrise.

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...ARK
NEAR TERM...AR
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...AR