646
FXUS62 KGSP 170538
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
138 AM EDT Mon Aug 17 2026

.WHAT HAS CHANGED...
Details were added for a potential severe weather threat on Monday
evening into the first part of the overnight.

Guidance is becoming more consistent in showing a cooling trend
next weekend.

The aviation forecast was updated to reflect the recent 06Z TAF
issuance.

&&

.KEY MESSAGES...
1. Another Heat Advisory is in effect Monday afternoon for the
SC Upstate, northeast GA, and the Charlotte Metro. Hot and humid
conditions persist most of this week, with little relief until
next weekend.
2. There is a Slight Risk for Severe Weather across western North
Carolina this evening. More seasonally-typical diurnal convection
continues for most of the week.

&&

.DISCUSSION...
Key message 1: Another Heat Advisory is in effect Monday afternoon for
the SC Upstate, northeast GA, and the Charlotte Metro.  Hot and
humid conditions persist most of this week, with little relief
until next weekend.

An unbearable week is on tap this fine Monday morning.  The most
recent water vapor imagery depicts broad subtropical ridging
extending across most of the southern CONUS, with the core
of a broad h50 anticyclone located over eastern Texas.  This
configuration shouldn`t change much through Wednesday morning,
though the core of the anticyclone may retrograde westward into
the Four Corners region, allowing heights to fall subtly over
the Carolinas.

A protracted pattern change will play out from Wednesday through
Saturday, as a deep upper low migrates from Manitoba eastward
into the Hudson Bay and northern Quebec, gradually wearing down
the subtropical ridge over the Southeast.  A weak cold front may
cross the area by Saturday, helping to further weaken the ridge.

As a result, hot and muggy conditions are expected for several
more days.  Today`s afternoon heat index forecast has most of
the low terrain seeing triple digits once again (though by
mid-afternoon, mixing of dry air into the PBL may result in
highly-variable dewpoints, so some locations may not see heat
index values quite as high as others); the remainder of the week
should feature afternoon heat index in the upper 90s or lower 100s
- still unbearable, but not quite what we`ve seen the last two
days. Should a cold front actually take place Friday or Saturday,
next weekend could turn out significantly cooler.


Key message 2: There is a Slight Risk for Severe Weather across
western North Carolina this evening.  More seasonally-typical
diurnal convection continues for most of the week.

As of around midnight, a few pesky convective cells have cropped up
over the Triad, within an area of 1500+ J/kg sbCAPE.  Another weak
cell has begun producing lightning over Polk County.  Surface obs
are suggestive of an axis of weak surface convergence extending
along and east of the NC Blue Ridge Escarpment...likely responsible
for triggering this late-breaking initiation.  With instability
on its last leg and winds forecast to weaken (thus resulting
in weakening convergence), don`t really expect much additional
activity, but will continue to monitor...

Otherwise, looks like a mostly benign morning and afternoon period
Monday, with a relatively suppressed solution from most of the CAMs.
The action will get going later than the typical diurnal period
on Monday, as a weakening cold front sweeps across the Tennessee
Valley, arriving in Appalachia by mid-evening, and triggering a
round of convection across the NC mountains.  The 00Z suite of hi-
res guidance isn`t especially consistent in how it handles coverage,
HRRR a with the late-evening timing limiting convective initiation;
the ARW and FV3 depict better coverage (over at least the NC zones),
while the HRRR, NAMnest, and NSSL-WRF feature scattered coverage
at best, and quickly kill it off east of the mountains.  The RRFS
is the lone outlier with impressive response all the way into the
Upstate and I-77 corridor.  Whatever convection does develop will
do so in a fairly impressive environment for this time of year -
featuring some 1000-1500 J/kg lingering MLCAPE, 20-25kts of deep
layer shear, and a notable mid-level dry slot evident in forecast
profiles.  This should support some degree of organization, and a
threat of damaging straight-line wind gusts, with the extent of the
threat mainly dependent on how much convection actually initiates.
The severe threat looks to diminish steadily as the system moves
east, with a progressively less-conducive-to-severe environment
farther and farther southeast.

The rest of the week looks more typical for August.  Both Tuesday
and Wednesday should be a tad more suppressed than usual, owing to
the suppressed postfrontal environment left in the wake of Monday
night`s FROPA and the lack of any good upper-air features this
far east; coverage may increase again by Thursday and Friday, as
the air mass steadily becomes more favorable for deep convection.
By Friday or Saturday, most ensembles still feature a cold front
arriving in the Carolinas.  This could increase both convective
verage and associated severe potential, but confidence in the
details is murky at this point.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Another benign summer night is in progress,
with mostly clear skies across the region, and light 1-4kt winds in
most locations.  A few garden-variety thunderstorms have redeveloped
along the I-40 corridor, bound for the Triad, but aren`t expected
to impact any of the TAF sites.  Convective debris should be swept
eastward over the next 1-2 hours, leaving most of the terminal
forecast area clear.  Some mountain valley fog/stratus may develop
again tonight, but in general, a steadier wind and drier air should
limit potential as compared to last night.

Quiet conditions are expected for the first half of the day Monday.
A shallow cu field should develop, but remain unperturbed the first
part of the afternoon.  An approaching cold front will incite late-
afternoon initiation over the NC mountains, potentially driving
convection east into the Piedmont and Upstate past sunset. Though
showers and storms are a better bet at KAVL and KHKY, confidence
remains lower on whether any convection will make it to KCLT or
the Upstate sites.

Outlook: Scattered showers and thunderstorms, with associated flight
restrictions, will be possible each afternoon thru Tuesday. Low
stratus and fog will be possible each morning, especially in the
mountain valleys.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory from noon today to 8 PM EDT this evening for
     GAZ018-026-028-029.
NC...Heat Advisory from noon today to 8 PM EDT this evening for
     NCZ070>072-082.
SC...Heat Advisory from noon today to 8 PM EDT this evening for
     SCZ008>014-019-104>109.

&&

$$

MPR