673
FXUS62 KGSP 171832
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
232 PM EDT Tue Sep 17 2024

.SYNOPSIS...
The remnants of the coastal low will meander over the region and
keep elevated rain chances across the area into tonight.  By
Wednesday, the remnant low will stall out over the Mid-Atlantic,
while high pressure begins to build into the region from the north
and west late in the week giving our region a dry weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
Key Messages:

1) Remnants of Potential Tropical Cyclone 8 will Continue to Weaken
as it Drifts Across the Western Carolinas

2) Low Rain Rates Will Prevent Any Flooding Issues

3) Patchy to Locally Dense Fog is Expected Overnight into Daybreak
Wednesday

As of 220 PM EDT Tuesday: Dreary weather will continue through much
of the near term thanks to the remnants of Potential Tropical
Cyclone (PTC) 8 meandering over the Carolinas while gradually
weakening. Mostly cloudy skies will continue through at least
Wednesday morning before cloud cover gradually thins out, becoming
scattered, Wednesday afternoon/evening. Patchy light rain/drizzle
continues over mainly the western and southern zones this afternoon
but the light precip shield will toggle more eastward this evening
into Wednesday. Thus, have low-end likely (55%-65%) to high-end
chance (45%-54%) PoPs confined to the western zones through the
early evening hours. Temps are being limited by both cloud cover and
precip this afternoon so highs should end up ~5-10 degrees below
climo. Maintained chance PoPs this evening into Wednesday across
much of the forecast area with spotty shower/drizzle activity
expected to linger. Precip has lead to patchy fog development at
times this afternoon and patchy fog is expected to become more
widespread overnight into Wednesday morning thanks to abundant low-
level moisture. Portions of the NC mountains may see dense fog at
times overnight into daybreak Wednesday with guidance showing the
potential for vsbys to drop to 1/4-1/2 mile. Fog should gradually
improve throughout the morning hours as mixing gets underway. Lows
Wednesday morning will end up ~4-9 degrees above climo thanks to
cloud cover and precip limiting radiational cooling. Although highs
will be noticeably warmer on Wednesday, they will remain ~2-4
degrees below climo.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 206 PM Tuesday: By tomorrow night, a weak closed upper low
centered over the Carolinas will open into a shortwave trough and
begin to lift north into New England as the synoptic pattern finally
becomes more progressive. Upper ridging that has been parked over
the Southern Plains will get nudged eastward as a potent northern
stream trough lifts across the Northern Rockies and into the
Northern Plains. As such, heights will slowly rise across the
Southern Appalachians as the upper low departs and ridging builds in
from the west. At least scattered showers will likely lingering
across the I-77 corridor into tomorrow night with a few isolated to
scattered showers during the day Thursday, although most of the
activity on Thursday will be focused over the mountains. Heading
into Friday, the upstream upper ridge axis will continue to slide
east into the Lower Mississippi Valley with further height rises
across the Carolinas and northeast Georgia. At the same time,
sprawling surface high pressure over the Hudson Bay will extend down
the east coast and help send a backdoor front through the area.
Dewpoints and PWATs will fall noticeably in the wake of the frontal
boundary as a drier airmass filters into the area. This will bring
an end to any lingering showers with the exception of a stray shower
over the mountains will convergence will be maximized along the
boundary as it drops south.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 223 PM Tuesday: A tranquil pattern will continue for much of
the extended forecast period as upper ridging migrates from the
Lower Mississippi Valley into the Southern Appalachians over the
weekend. Surface high pressure extending form New England down the
spine of the Appalachians will keep dry air in place. This will
support healthy diurnal temperature swings of 20-25 degrees each day
as deep mixing within the dry airmass promotes highs in the low 80s.
Several nights of decent radiational cooling is also expected with
overnight lows falling into the upper 50s to low 60s.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Another messy 18Z TAF forecast can be
expected thanks to the remnants of Potential Tropical Cyclone (PTC)
Eight meandering over the western Carolinas. Seeing BKN to OVC IFR
to MVFR clouds across the terminals this afternoon with -SHRA
confined to the SC Upstate terminals and KAVL. Have TEMPOs through
22Z across the SC Upstate terminals for -SHRA and IFR cigs with
prevailing -SHRA  and MVFR cigs at KAVL through 00Z. Most terminals,
except KAVL, will likely see a brief period of drier conditions this
evening before moisture returns overnight. Both cigs and vsbys
should gradually lower late this evening into the overnight hours
with the return of -SHRA. Thus, have PROB30s across all terminals
overnight to account for LIFR/IFR vsbys and cigs. -SHRA looks to
linger through at least Wednesday morning, which will act to keep
LIFR to IFR cigs and vsbys around so have TEMPOs during the morning
hours on Wednesday for all terminals. Restrictions will once again
be slow to improve on Wednesday, but by the afternoon and early
evenings hours vsbys/cigs should gradually improve to MVFR to VFR
levels. Wind direction will be primarily NE across the SC Upstate
terminals through Wednesday while winds at KHKY and KCLT will
generally be E/ESE. Winds at KAVL will generally have a N`ly
component and will be VRB at times.

Outlook: A weak upper low will lift northeast late Wednesday into
Thursday. Restrictions return again Wednesday night into Thursday.
On Friday, sfc high pressure builds into the area from the north
allowing drier weather and VFR conditions to return.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...AR
SHORT TERM...TW
LONG TERM...TW
AVIATION...AR