383
FXUS62 KGSP 131047
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
647 AM EDT Sun Sep 13 2026

.WHAT HAS CHANGED...
The aviation discussion was updated for the 12Z TAF issuance.

&&

.KEY MESSAGES...
1. Scattered showers and some embedded thunderstorms will remain
possible through daybreak as a weak front crosses the area. Behind
the front, quiet weather is expected through Monday.
2. A backdoor cold front should arrive late Monday, but confidence
is limited on what the impact will be as it moves through and
what happens during the middle part of the week.

&&

.DISCUSSION...
Key message 1: Scattered showers and some embedded thunderstorms
will remain possible through daybreak as a weak front crosses the
area. Behind the front, quiet weather is expected through Monday.

The latest satellite imagery shows the mid-level moisture gradient
accompanying a short wave axis moving slowly east from east TN to
the western Carolinas late this evening. A broken band of showers
with a few thunderstorms, mainly east of I-77, was moving off to
the east along with a plume of deeper moisture associated with a
weak low level jet. Until the moisture gradient crosses the region,
it remains possible that persistent showers with high precip rates
could produce enough rain in a short period of time, resulting
in flooding. However, that window was closing steadily. The radar
trend is definitely downward in coverage and intensity. We continue
to monitor, particularly over the urban areas. Meanwhile...precip
probs will steadily drop from the west and end around sunrise with
the passage of the short wave axis. The widespread rain in the
past 24 hours and the remaining low level moisture suggest that
it will remain murky through sunrise. Patchy dense fog looks like
a decent bet, but whether or not coverage improves to the point
where a Dense Fog Advisory will be needed remains to be seen.

In the wake of the wave, it should be relatively quiet on Sunday as
slightly drier air moves in, but the environment will be unfavorable
for deep convection with no forcing, a weak cap, poor lapse rates,
and a lack of buoyancy. There could be a few ridgetop showers,
as per usual, particularly on Monday as the situation gets a bit
more favorable over the mtns. A weak front to the north is not
expected to reach this far south before late Monday. Temps will
warm up to five degrees over normal both days, but nowhere near
enough to heat advisory criteria.


Key message 2: A backdoor cold front should arrive late Monday,
but confidence is limited on what the impact will be as it moves
through and what happens during the middle part of the week.

A strong short wave is expected to pass by to our north on Monday,
driving a back door cold front southward and across our region,
but probably not until the evening hours. As it stands right now,
the model guidance shows little in the way of response, which is
not a surprise given the weak cap and lack of buoyancy across the
region Monday evening as it passes. The more interesting part of
the forecast happens behind the front starting on Tuesday. An
upper anticyclone drifts in from the west but remains centered
over the TN Valley region. The upper ridge will support sfc high
pressure moving slowly from the lower Great Lakes to the Canadian
Maritimes from late Monday through Tuesday, then ridging down
from the northeast into Wednesday. There are some indications
of weak cold air damming developing on Tuesday, though without
the benefit of precip or a light easterly flow of moisture, temps
might still climb a few degrees above normal. We only mention this
because if some moisture were to move in from the east, the temp
forecast could be several degrees too warm. For the time being,
the NBM indicates that temps are likely to reach at least normal
(mid-80s) east of the mtns both Tuesday and Wednesday.  As we
get into the second half of the week, moisture lingers over the
mtns each day, suggesting a chance of diurnal showers and storms
each day Thursday through Saturday. As we get into next weekend,
confidence is very low owing to the presence of a cutoff low near
the Southeast Coast indicated by the GFS, so all bets are off.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Widespread low stratus and fog will impact
all TAF sites through daybreak with IFR/LIFR cigs and locally
dense fog possible. Mountain valley fog and low stratus will keep
restrictions at KAVL as well. Fog will mix out shortly after
daybreak, while low stratus will lift and scatter during the same
time frame. Expect VFR conditions to prevail through much of the
daytime period as a result. Light winds will be out of the south to
southwest or variable through daybreak with a shift to the west to
northwest by the morning hours. A few low end gusts are likely at
KAVL during the afternoon. Guidance hints at another round of
mountain valley fog and low stratus, which could impact KAVL
overnight tonight.

Outlook: Quiet conditions are expected to persist through early
Monday. A second round of showers may develop on Monday afternoon
and evening, but confidence is low, and coverage may only be
isolated.

&&

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

&&

$$

CAC/PM