-- Discussion containing changed information from previous version are highlighted. --
411
FXUS62 KGSP 221029
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
629 AM EDT Sun Sep 22 2024

.SYNOPSIS...
High pressure will linger across the region through the weekend
helping keep temperatures above normal. A more moist airmass will
spread over the area on Monday and linger through at least mid-week.

&&

.NEAR TERM /THROUGH TONIGHT/...
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As of 620 am EDT: An upper ridge axis to our west will become
centered over the Appalachians by the end of the period. Fog/low
stratus remains largely confined to the mountain valleys this
morning, and the imminent sunrise suggests this is unlikely to
expand much beyond current coverage. Otherwise, another hot and
relatively muggy day, with max temps expected to average almost
10 degrees above climo. Moderate destabilization, with forecast
soundings indicating an uncapped environment will create some
potential for spotty diurnal convection late in the day...
especially across the western half of the area, where 20-30 PoPs
are advertised. Any convection should diminish by late evening,
although some activity originating from a frontal zone across
the Ohio Valley could wander toward the southern Appalachians
toward daybreak Monday. Min temps will be 5-10 degrees above
normal.
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&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 3:05 AM EDT Sunday: The short-term fcst picks up at 12z on
Monday with broad upper ridging still in place over the Southeast.
The upper ridge is expected to linger over our area thru the period,
though it does get suppressed by an embedded upper trof that rides
up and over the ridge from the SW on Tuesday. At the sfc, a complex
low will develop over the Ohio River Valley and move a broad area
of deeper moisture SE and down the spine of the Appalachians and
into our fcst area as the period begins early Monday. This moisture
is expected to linger for the rest of the period and spread further
SE early Tuesday. By the end of the period early Wednesday, another
low will spin up over the Ohio River Valley and bring another cold
front to our doorstep from the west. As for the sensible fcst, I
bumped up precip chances across our northern zones for both Monday
and Tuesday afternoon/evening. In addition to showers, we could also
see some thunderstorms as some amount of instability will be present
over the fcst area during the afternoon/evening. High temperatures
will moderate on Monday and Tuesday under increased cloud cover,
yet still remain above climatology across most of the CWA.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 3:15 AM EDT Sunday: The extended fcst picks up at 12z on
Wednesday with upper ridging still lingering over the far SE
CONUS as broad upper trofing amplifies over the central CONUS.
The operational models appear to be coming into better agreement
wrt the evolution of the upper trof during the first part of
the period. The majority of the long-range guidance has a fair-
ly large upper low spinning off the backside of the trof over
the central CONUS on Wednesday, while the trof itself continues
to translate eastward with the trof axis passing to our north
early Thursday. On Friday, another large upper low is expected
to quickly dive southward and over the New England area as the
above-mentioned upper low lingers just to our west. Beyond this
point, it is difficult to predict how these lows will interact
with each other, but most of the guidance has the central CONUS
upper low remaining to our west thru the weekend. At the sfc,
a low pressure system will lift north over the eastern Great
Lakes and move another cold front into our fcst area later on
Wednesday. It`s looking increasingly likely that the front will
stall out over our area while broad high pressure remains well
to our NW for Thursday and Friday. At the same time, a robust
tropical low from the Gulf of Mexico will track north and over
our area as early as Friday. We will need to see how consistent
the long-range guidance is over the next few days with this sys-
tem before we can have much confidence wrt how it will impact
our area.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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At KCLT and elsewhere: Derived satellite imagery reveals low
stratus/ possible fog very close to KAVL, so will plan on a tempo
for at least MVFR restrictions through 14Z. Still can`t rule out a
brief restriction this morning at KHKY, although that window is
quickly closing. Otherwise, VFR will continue through at least this
evening. Development of spotty diurnal convection is expected late
this afternoon/evening, especially across the western half of the
area. Coverage is still expected to be isolated and therefore not
worthy of a TAF mention. Generally light/variable winds early this
morning are expected to gradually turn the dial from NW=>NE=>E
from late morning through the evening, while speeds will mostly
remain 5 kts or less. Signals in statistical guidance suggest
increased chances for low stratus development at the western NC
terminals late tonight/early Monday. The 12Z TAFs feature
development of MVFR conditions at KAVL and KCLT, with IFR at KHKY
between 08-12Z.

Outlook: A weak cold front will slowly approach from the west early
next week before tracking over the area on Thursday. Chances for
diurnal showers and thunderstorms will increase Monday and remain
elevated through at least Thursday. Mountain valley fog/low stratus
may develop each morning around daybreak.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...JPT
NEAR TERM...JDL
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...JDL