684
FXUS62 KGSP 211048
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
648 AM 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 TONIGHT/...
As of 640 am: Fog and low stratus, including patchy dense fog
continues to steadily expand across the forecast area this morning,
and may continue to expand for another hour or so before insolation
increases. A Dense Fog Advisory remains unnecessary, but a Special
Weather Statement for patchy dense fog may be in order.

Otherwise, an upper ridge extending from an anticyclone over Texas
will continue to nudge into the forecast area through the period,
resulting in a continuation of unseasonably hot conditions, with max
temps today expected to again be around 5 degrees above normal.
Humid conditions will also persist, and the atmosphere is expected
to destabilize to the tune of around 1500 J/kg of sbCAPE this
afternoon. Spotty diurnal convection is expected to develop within
this air mass, especially in areas along/near the Blue Ridge
escarpment. 20-30 PoPs are advertised in these areas.

An area of height falls will briefly brush the eastern part of the
CWA this evening, and most short term and convection-allowing model
guidance allows some scattered convection to move into the western
NC Piedmont from the northwest between 00-06Z Sunday. This warrants
a period of 20-30 PoPs across these areas during that time.
Otherwise, min temps will again be at least a category above normal.

&&

.SHORT TERM /SUNDAY 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 /12Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Low stratus and/or fog has finally become
widespread in the mountain valleys this morning, with LIFR being
reported at KAVL. This should dissipate by 14Z. VFR generally
prevails at the other sites, but the latest guidance is hinting at
the potential for low stratus to expand around sunrise before
dissipating by late morning...indicating that KGMU/KGSP/KCLT could
see some restrictions early in the period. Although this is
plausible, we`re not seeing this in observational data at this
point, so the potential has been addressed with tempo/s for MVFR fog
and FEW/SCT IFR layers. Otherwise, winds will become light southerly
by late morning. Isolated diurnal convection is expected this
afternoon and evening, but coverage is again expected to be too
sparse to warrant a TAF mention at any site. Some fog and low
stratus may redevelop toward daybreak Sunday, and this is hinted at
in the 12Z TAFs.

Outlook: No appreciable return of moisture or precip chances
expected until early to middle of next week. Daybreak restrictions
could recur each morning especially in mountain valleys.

&&

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

&&

$$

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