359
FXUS62 KGSP 211737
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
137 PM EDT Sat Sep 21 2024

.SYNOPSIS...
High pressure will linger over the region through the weekend with
temperatures warming above normal. A more moist airmass will move
into our area from the north early next week and linger through mid-
week increasing rain chances.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 135 PM: Despite an upper ridge extending from an anticyclone
over Texas settling over the area today, a weak short wave crosses
the area which may bring enough forcing to combine with weak
instability and increased shear to produce isolated convection this
afternoon and evening. The CAM guidance is decidedly in 2 camps with
either no convection or isolated convection. Have retained the
isolated convection near and along the Blue Ridge given the upstream
convective activity. This feature moves across the NC Piedmont this
evening into the overnight bringing the potential for isolated
convection there. Should be another round of mountain valley fog
with patchy fog elsewhere. Lows will be 5 to 10 degrees above normal.

The upper ridge remains over the area Sunday with increasing
thickness values. Warming mid levels should limit instability and
put a lid on convection. Have a dry forecast for now. Highs will be
around 10 degrees above normal.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 3:05 AM EDT Saturday: The short-term fcst picks up at 12z on
Sunday 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. At the sfc, broad high pressure
will be in place over the Southeast as the period begins. As we move
into Monday, 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. This moisture is expected
to linger for the rest of the period and spread further SE by early
Tues. As for the sensible fcst, I still expect Sunday to be mostly
dry with precip chances increasing on Monday especially over the
northern half of our CWA. In addition to showers, we could also
see a few weak thunderstorms as some amount of instability will
likely be present over the fcst area during the afternoon/evening.
Temperatures should peak on Sunday with highs expected to approach
and/or exceed 90 degrees across most of our Upstate zones, and
mid to upper 80s over our NC Piedmont zones. Temps will moderate
on Monday under increased cloud cover.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 2:55 AM EDT Saturday: The extended fcst picks up at 12z on
Tuesday with upper ridging still lingering over the SE CONUS as
broad upper trofing amplifies over the central CONUS. Over the
next few days, the evolution of this trof varies considerably
between the operational models. The majority of the long-range
guidance has the trof axis passing just to our north by late
Wed and then morphing into a large closed h5 low on Thursday.
This upper low then lingers somewhere over the Atlantic/New
England Coast thru the end of the week and into the weekend.
The current GFS solution is quite a bit different and still
appears to be an outlier. At the sfc, weakening high pressure
will still be lingering to our south as the period begins. A
broad area of deeper moisture associated with a complex low
pressure system will also be present just to our north. As we
move into Wednesday, another cold front is expected to gradually
approach our area from the west and move thru our area later in
the day. In its wake, broad high pressure will likely spread
back over the fcst area from the NW and linger into the weekend.
It should be noted that by the end of the period next Saturday,
most of the long-range guidance has some sort of tropical system
strengthening over the Gulf of Mexico and tracking northward to-
wards our area just beyond day 7. Temperatures will moderate thru
the period with highs expected to drop just below climatology by
the end of the week.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Low VFR Cu, along with cirrus, will remain
over the area this afternoon. Isolated convection is expected this
afternoon and evening, but coverage will again be too sparse to
warrant a TAF mention at any site. A generally light SW wind becomes
calm to light and variable overnight. Expect fog and low stratus
again in the mountain valleys with patchy coverage elsewhere. Have
MVFR TEMPO IFR Vsby/LIFR cigs again at the most likely locations of
KAVL and KHKY. This should dissipate before mid morning with some
low VFR Cu again developing. Light W to NW wind on Sunday.

Outlook: A weak frontal system approaches the area and stalls over
or near the area through Thursday bringing the potential for diurnal
convection. Daybreak restrictions could recur each morning
especially in mountain valleys.

&&

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

&&

$$

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