016
FXUS62 KGSP 240433
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1233 AM EDT Tue Sep 24 2024

.SYNOPSIS...
A moist and cooler airmass will remain in place across the forecast
area through mid-week. A tropical system is expected to strengthen
over the Gulf of Mexico, making landfall late Thursday and affecting
the Carolinas on Friday.

&&

.NEAR TERM /THROUGH TODAY/...
As of 12:25 AM EDT Tuesday: We`re still seeing some isolated showers
over the NC Piedmont (just west of the CLT area) and near the NC/TN
border. The showers/cells near CLT have grown taller over the past
half hour or so, but have yet to produce any lightning. The latest
CAMs still have some shower activity lingering thru the overnight
hours, mostly across our NC zones. Another round of low stratus and
patchy fog will also likely develop from NE to SW across the area
overnight. This will help keep lows around 10 degrees above normal.

Otherwise, Tuesday should see a similar scenario as today with
morning stratus slowly eroding and lifting from SW to NE through
the day. Moderate instability with up to 35 kts of effective bulk
shear expected as well. There may be better DCAPE Tues afternoon
though. Expect good diurnal convective coverage during the aftn
with a few severe thunderstorms. Highs will see a similar pattern
as well with cooler temps where the stratus burns off latest.
Highs will be around 5 degrees above normal.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
As of 155 PM EDT Monday: By Tuesday evening, a potent upper low will
be in place over the Ozarks, with the western Carolina sandwiched
between its eastern periphery and a deteriorating ridge off the
Atlantic coast.  On the east side of a narrow baroclinic zone
stretching from the Mississippi Delta region up into the Tennessee
Valley, moisture will stream into the forecast are out of the
southwest, maintaining cloud skies and at least scattered afternoon
on Wednesday.  As low-level flow turns around out of the ESE late
Wednesday and into Thursday, moisture will gradually diminish,
resulting in a brief reprieve from the wet conditions. For what
showers do develop on Wednesday, some thunder will be able to mix
in, given 1000-1200 J/kg sbCAPE.  20kts or so of deep layer shear
may support some loosely-organized multicell clusters, and,
especially as dry air begins to build in aloft, perhaps some
downburst wind threat.

Thursday will feature the slow approach of the remnants of Potential
Tropical Cyclone 9.  Models are in good agreement at this time on
the low moving inland over the Florida Panhandle and tracking NNE
into central Georgia through late in the day Thursday.  The first
upper-level moisture associated with PTC 9 will arrive as early as
Thursday morning...but in terms of the deeper moisture needed to
spur heavy rain...that`s not depicted arriving earlier than late
Thursday afternoon, or possibly past the end of the short term
period Thursday night.  Thus, more appreciable rainfall doesn`t
appear likely through the end of the day Thursday.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 204 PM EDT Monday: Thursday night and the first part of Friday
will give us our taste of whatever impacts PTC 9 brings. Long-range
ensembles remain split into two camps.  The dominant group of LREF
members curve the post-tropical low westward as it interacts with
the preexisting upper low still churning over the Ozarks.  This
results in generally lower QPF response for the western Carolinas,
and weaker winds.  The secondary group of LREF members, however,
depicts either less interaction with the low, or a low shifted a
little farther eastward, bringing the remnant low directly over
northeast Georgia and the western Upstate.  Such a solution would
result in potentially significant rainfall across parts of the
Upstate.  Forecast soundings for the Upstate, from both the
operational GFS and GDPS, also feature low-level winds in excess of
45kts.  The 850mb charts are even more dire.  Although the
configuration won`t be favorable for mixing this wind down to the
surface in its entirety, it`s a hint that strong winds may also be a
problem Thursday night and Friday.  The current NHC forecast calls
for no more than a 10% chance of tropical-storm force winds for the
Upstate...and that seems quite reasonable at this time.

Friday night, whatever is left of the post-tropical low will either
deteriorate in a zone of unfavorable dynamics over central Virginia,
or be absorbed into the preexisting Ozark low (depending on whether
the eastern or western track pans out).  Behind it, an extensive
layer of dry air aloft is progged to push into the area from the
south, associated with weak ridging.  Despite this, weekend
temperatures look to stay in the low- to mid-70s.  The Ozark low,
meanwhile, should remain in place somewhere over the Deep South.
Consensus is, though, that it`ll remain far enough west as to
preclude any impacts for our area.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Mostly MVFR/VFR cigs are noted across the
terminals as of 02Z. Some scattered showers linger across the
northern and western North Carolina mountains and the northern North
Carolina Piedmont as of 02Z. Showers should linger through the
overnight hours, especially across western North Carolina. Thus,
only have TEMPOs at KCLT and KHKY during this timeframe as these
sites have the best potential to see activity. Maintained dry
conditions elsewhere as confidence is too low for TEMPOs.  Winds
will generally be calm to light and VRB into the overnight hours.
Another round of IFR to LIFR low stratus is expected to develop
overnight into early Tuesday morning so have TEMPOs across all
terminals to account for this. Patchy fog may develop as well but
confidence on IFR to MVFR vsbys is lower. Fog should mix out by 13Z-
14Z Tuesday but cigs will once again be slow to improve, especially
at KHKY and KCLT. Another round of scattered thunderstorms is
depicted by the high-res guidance so have PROB30s across all
terminals Tuesday afternoon and evening. Winds will gradually turn
S/SSW Tuesday morning into Tuesday afternoon.

Outlook: A slowly approaching weak cold front stalls west of the
terminals on Wednesday, keeping the chance for diurnal showers and
thunderstorms around. Fog/low stratus may develop each morning,
especially in the mountain valleys. Confidence is increasing that a
tropical cyclone will bring heavy rain and the potential for strong
winds Thursday into Friday before moving out of the area Friday
night into Saturday.

&&

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

&&

$$

SYNOPSIS...MPR
NEAR TERM...AR/JPT
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...AR/JPT