224
FXUS62 KGSP 201028
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
628 AM EDT Sun Sep 20 2026

.WHAT HAS CHANGED...
Updated the aviation discussion for the 12z TAF issuance.

&&

.KEY MESSAGES...
1. Scattered showers and thunderstorms are expected each afternoon
and evening through Monday. A few of the storms may become severe,
with damaging wind gusts and excessive rain being the main threats.
2. A notable pattern change is expected during the middle of the
upcoming week that should bring cooler temperatures to our area.

&&

.DISCUSSION...
Key message 1: Scattered showers and thunderstorms are expected each
afternoon and evening through Monday. A few of the storms may become
severe, with damaging wind gusts and excessive rain being the main
threats.

Conditions will remain unsettled over the next few days as flat upper
ridging centered over the southern Plains interacts with a weak upper
low over the Florida peninsula and eastern Gulf. This upper pattern
coupled with a very broad region of low-level convergence, will help
keep ample deep-layer moisture over the Southeast and fuel diurnal
showers and thunderstorms both Sunday and Monday. Activity is expected
to initiate over the mtns each day and then spread S/SE as the day/
evening progresses. Overall, it`s looking like we will see better
coverage on Monday, especially over the NC Piedmont and eastern SC
Upstate. Some of these storms will likely become strong to severe,
with damaging wind gusts and excessive rain being the main threats.
It`s still looking like strong to severe storms will be more likely
on Monday than Sunday. As such, SPC keeps their Marginal Risk area
just to our north on Sunday, but puts a portion of the NC mountains
in a Slight Risk for Monday. This appears reasonable with greater
sfc-based CAPE expected on Monday and sufficient dCAPE each day. In
addition, the risk for excessive rain also increases as warm cloud
depth increases and storm motions are likely to be fairly slow. As
such, WPC has their Marginal Risk for Excessive Rainfall expand
across our area each day thru Tuesday. As for temperatures, they
will remain above normal thru at least Monday. Values will moderate
somewhat by Tuesday, assuming increased cloud cover and rain
coverage, but highs are still fcst to be a couple degrees above
normal for mid to late Sept.


Key message 2: A notable pattern change is expected during the middle
of the upcoming week that should bring cooler temperatures to our
area.

Early in the coming week, the northern stream becomes more blocky
over the central CONUS as a mid/upper low slides underneath stout
upper ridging. This results in a Rex-type blocking pattern centered
to our north by mid-week. The upper low is expected to strengthen/
expand towards the end of the week and begin to move offshore by the
weekend. At the surface, cyclogenesis off the Mid-Atlantic coast is
expected to bring a back-door cold front southward and thru our fcst
area on Tuesday. At the same time, very broad sfc high pressure will
park itself to our north over Ontario and Quebec helping to establish
a cold-air damming wedge on Wednesday that will likely persist thru
the end of the week. The resulting cool NELY flow and shower potential
will help keep temperatures about 8 to 10 degrees below normal for the
latter half of the week. The wedge will likely weaken by Friday as the
surface low lifts further NE and drier air works its way into our area
from the west. Nonetheless, temperatures are expected to remain below
normal thru next weekend with shower chances diminishing each day.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Winds remain light and VRB through the period
across most terminals. BR/FG at KAVL through at least 13z, so
extended the TEMPO. Higher cloud deck is keeping cigs from dropping
into IFR across the Upstate sites. Could still see a brief dip into
MVFR cigs through early afternoon at these locations. TSRA possible
at a few sites this afternoon, prompting another PROB30, except at
KCLT/KAND where confidence is lower. VFR cigs and calm winds return
after 00z, except KAVL/KHKY for BR/FG, as usual.

Outlook: Shower and thunderstorm chances continue each afternoon
through Tuesday. Mountain valley fog and low stratus possible each
morning.

&&

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

&&

$$

CP/JPT