-- Discussion containing changed information from previous version are highlighted. --
923
FXUS62 KGSP 180408
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1208 AM EDT Wed Sep 18 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 TODAY/...
-- Changed Discussion --
Key Messages:

1) Remnants of Potential Tropical Cyclone 8 will spin and wobble
over the forecast area, resulting in plenty of clouds and spotty
light rain and drizzle.

2) Low Rain Rates Will Prevent Any Flooding Issues

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

As of midnight EDT Wednesday: the forecast remains on track. No
changes needed, other than freshen up the hourly temps and dewpts
to reflect latest obs.

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 evening but the light precip
shield will toggle more eastward later this evening into Wednesday.
Thus, have high-end chance (45%-54%) PoPs confined to the western
zones through the early evening hours. 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 evening 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.
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT 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 /04Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Messy 00Z TAF forecast period thanks to the
remnants of Potential Tropical Cyclone (PTC) Eight meandering over
the western Carolinas. Seeing mostly BKN to OVC IFR to MVFR clouds
across most of the terminals this evening (although KAND has gone
VFR) with -SHRA confined to KGSP, KGMU, and KAVL. -SHRA should
gradually expand eastward back towards KHKY and KCLT later this
evening into early Wednesday morning. Both cigs and vsbys will
gradually lower this evening into the overnight hours with the
return of -SHRA. Thus, have TEMPOs and prevailing -SHRA or VCSH
across the terminals overnight to account for LIFR/IFR vsbys and
cigs. -SHRA should linger through daybreak Wednesday which will act
to keep LIFR to IFR cigs and vsbys around during the morning hours.
Restrictions will once again be slow to improve throughout
Wednesday, but by the afternoon and early evening 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/ARK
SHORT TERM...TW
LONG TERM...TW
AVIATION...AR