499
FXUS62 KGSP 171037
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
637 AM 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 today and 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.

&&

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

1) The remnants of Potential Tropical Cyclone Eight is gradually
weakening this morning as it drifts across northern SC.

2) Flood Watch for Flash Flooding remains in Effect for the
Charlotte Metro Area through 8 AM this morning.

3) Heaviest rain going forward is expected to be along the eastern
NC Escarpment and adjacent foothills, but not enough to warrant
expanding the Flood Watch.

As of 6:30 AM EDT Tuesday: The remnants of Potential Tropical
Cyclone (PTC) Eight continues to gradually drift inland over the
Carolinas and weaken, now centered just south of the Charlotte
metro area. Rain rates continue to diminish, and the Flood Watch
will likely be able to expire on schedule.

The rest of the day, the story will be a generally low overcast
sky with spotty light rain lingering across much of the forecast
area. The remnants of PTC 8 will stall over the Upstate this
aftn, then wobble east and then north tonight. Additional showers
are progged to form mainly on the west and north sides of the
circulation, which means highest PoPs will extend from the northern
Upstate thru the Central and Northern NC Mountains. The southern
Upstate and the Charlotte area should be on the drier side of the
circulation, but still could see a few periods of light rain or
showers. Highs will be well-below normal under the clouds.

Tonight, with the low still wobbling over the area, continued cloudy
skies and showery conditions expected. QPF should be light. Lows
will be slightly above normal.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 135 AM EDT Tuesday: The leftovers from Potential Tropical
Cyclone 8 will evolve into a weak closed upper low centered
right over the CFWA and meander over the area through the
day Wednesday into Wednesday night. The combination of the
closed upper low and above-normal PWAT values (~1.50"-1.75")
will support elevated coverage of showers, which is represented
well with likely PoPs (55%-70%) over the NC mountains and chance
PoPs (25%-54%) elsewhere. Model guidance suggests a few hundred
joules per kilogram of instability may develop across the CFWA
during peak heating Wednesday, which could lead to a few embedded
thunderstorms as well. Rain chances will linger into the nighttime
period Wednesday as the upper closed low begins to open up into a
shortwave trough and gradually lift into the northeastern CONUS
by late Thursday. Dry air entrainment will begin to take place
as upper/mid-level north-northwesterly flow filtering in as the
shortwave trough axis shifts east of the CFWA. Lingering showers
may remain in place over the favorable upslope regions over the
mountains late Thursday, but the expectation is that rest of the
area will dry out by the end of the forecast period. Temperatures
are expected to remain a few ticks below normal for afternoon
highs both Wednesday and Thursday, while overnight lows run at or
slightly above normal thanks to extensive cloud cover and increased
rain chances.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 300 AM EDT Tuesday: Changes in the synoptic pattern becomes
evident in the extended forecast period as any lingering upper
troughiness begins to lift out the region and a stout upper
anticyclone sets up shop over northern Mexico and the Southern
Plains. Over the weekend, the upper anticyclone will pivot eastward
and allow for gradual height rises to move into the southeastern
CONUS. At the same time, weak surface ridging will result in a drier
airmass and lead to much improved sensible weather conditions with
afternoon highs and overnight lows at or slightly below normal
for much of the medium range. The upper ridge over the central
CONUS will begin to breakdown and large scale changes start to
take place beyond D7, but the current D4-D7 deserves two thumbs up.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: The remnants of Potential Tropical Cyclone
Eight will stall over the Upstate today, keeping plenty of low
clouds and areas of mainly light showers or drizzle around. Rain
coverage should generally decrease thru the day, then tick up
somewhat late aftn into this evening, mainly across the Upstate
and southern NC mountains. KCLT will be on the east the remnant
low today, resulting in winds favoring an ESE direction (although
it will be close to due easterly). KCLT will likely see a lull in
precip by late morning thru the aftn, but IFR cigs are expected
to persist thru the day with some potential for improvement to
MVFR late aftn. Cigs should lower across the area this evening,
with possibly widespread LIFR conditions by daybreak Wednesday,
as the low continues to spin.

Outlook: A weak upper low will linger over the Carolinas Wednesday
before gradually weakening and lifting NE late Wednesday into
Thursday. Should see some improvement in cigs by Wednesday aftn,
but a return of more restrictions 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...Flood Watch until 8 AM EDT this morning for NCZ057-070>072-082.
SC...None.

&&

$$

SYNOPSIS...CAC
NEAR TERM...ARK
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...ARK