396
FXUS62 KGSP 140020
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
820 PM EDT Sat Jun 13 2026

.WHAT HAS CHANGED...
Increased confidence for isolated severe weather on Sunday.

&&

.KEY MESSAGES...
1. Highly isolated showers and thunderstorms this evening, then
greater coverage of storms across the area Sunday. Confidence
has increased that thunderstorms will pose a damaging wind threat
Sunday, with some potential for swaths of tree and minor structural
damage, mainly in Northeast Georgia and the western Upstate. Hot
and muggy through Sunday, but cooler Monday.
2. Drier and slightly below-normal temperatures Monday and early
next week, with moisture and rain chances increasing in the second
half of the week.

&&

.DISCUSSION...
Key message 1: Highly isolated showers and thunderstorms this evening,
then greater coverage of storms across the area Sunday. Confidence
has increased that thunderstorms will pose a damaging wind threat
Sunday, with some potential for swaths of tree and minor structural
damage, mainly in Northeast Georgia and the western Upstate. Hot
and muggy through Sunday, but cooler Monday.

Subtle stalled frontal boundary across the Carolinas this afternoon
mainly evident in a gradient of PWAT and dewpoint from the mountains
to the Piedmont, but very subtle. We appear to lack any significant
forcing mechanism this afternoon aside from whatever convergence
is present along the front. Profiles are relatively dry aloft,
similar to yesterday, when convection seemed only to fire with aid
of a cold pool boundary and/or shortwave, which are not present
this afternoon. Thinking is the dry profiles make deep convection
generally unlikely, though SBCAPE of 1500-2000 J/kg is analyzed
per SPC Mesoanalysis, along with 1000+ DCAPE and less than 20
kt of 0-6km shear. Highly isolated thunderstorms remain possible
this afternoon and evening. It would appear if any fire, they
could pose a threat of strong to severe 40-60 mph winds. A few
isolated showers/storms could develop this evening over the
lower/eastern Piedmont (Union SC to Union NC) well after peak
heating, if sea breeze moves as far inland as some models
depict. Heat indices in the lower Piedmont are likely to top 100
this afternoon but any instances of 105 should be isolated.

Sunday, as upper low swings across Ontario within a broader
trough, a cold front will advance across the Ohio Valley during
the afternoon. The current stalled front looks to lift north and/or
wash out by morning. Moisture advection ahead of the front should
bring higher PWATs into our area. 0-6km shear will rise to 20-30 kt
in the stouter upper flow around the trough, with SBCAPE similar
if not higher owing to temps trending slightly warmer and more
humid again. DCAPE and sfc-midlevel delta-theta-e values remain
high in the morning, though the increasing lower level moisture
diminishes that over the course of the day. CAMs have largely
depicted a prefrontal trough promoting convective development to
our west and some degree of upscale growth along that axis, and/or
along cold pools. Concern for organized storms, posing primarily
a wind threat, has increased. CAM consensus is best over north
GA into the western Upstate. SPC upgraded most of our CWA to a
Slight Risk on the midday Day 2 update today, with the initial
GA/SC area of concern being combined with an expanded risk areas
in the Mid-Atlantic. The CAM consensus still could shift and thus
changes in placement remain possible when this period becomes Day
1 tonight. Looks like another day with heat indices in the 100-104
range along and southeast of I-85. Convection looks likely to end
soon after sunset assuming the activity will mainly be cold-pool
driven; a few showers could keep going later into the night along
the TN/NC border with NW flow developing, in areas not worked over
by convection earlier in the day.


Key message 2: Drier and slightly below-normal temperatures Monday
and early next week, with moisture and rain chances increasing in
the second half of the week.

The surface cold front should settle past the area Sunday night and
confidence has increased slightly that we will be on the cool/dry
side of the front Monday, such that PoPs now remain 15% or less
through the afternoon. Temps return to near normal and heat index
should remain well below 100. The front will remain stalled to our
south for a day or two. Small PoPs return to the forecast in some
of our SE zones at times Monday night through Wednesday, which
are plausible in that as the base of the upper trough approaches
from the west, it could initiate warm upglide over the front.
These chances also simply could be explained by old model runs,
which showed the front not clearing the area before stalling, being
part of the blend. Most likely those periods will be dry, especially
in the northern zones. Temperatures trend still cooler Tuesday,
topping out a few below normal, returning to near normal Wednesday.

Confidence decreases for the second half of the week as the front
may interact with a weak disturbance exiting the western Gulf,
and/or as the next upper trough approaches from the NW along
with a cold front. A return to more active weather, with periodic
chances for showers/storms, appears to be a good bet. A majority of
guidance depicts a tight gradient over the area Thursday ahead of
the trough, which resulted in robust gusts falling out of the NBM,
and could indicate some organized severe weather threat around
that time. Confidence is low, as noted. Currently not expecting
heat indices to be a concern.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Convection has remained at bay across most of
the region except for very isolated storms focused near the southern
Blue Ridge Escarpment. While an additional pop-up shower or storm
cannot be ruled out through the rest of the evening, coverage and
thus confidence of it impacting any specific terminal is well too
low to mention in 00Z TAF. Several Convection-Allowing Models (CAMs)
have advertised the NC Piedmont as being an area for potential
development, satellite trends shows this would likely occur just
east of KCLT where a more robust cumulus field has recently
developed. Otherwise, winds will generally be light and variable
tonight. Radiation fog setup possible at KAVL.Kept the TEMPO MVFR
vsby toward daybreak, but confidence has trended lower since
precipitation missed the terminal. A W-SW wind will strengthen
to 5-10 kt during the mid to late morning and and to 10-15 kt
with gusts near 20 kt developing during the afternoon. Forecast
soundings show the potential for at least occasional gusts as
high as 25 kt during the mid to late afternoon. An eventual
wind shift out of the W or even W-NW is likely in the late
afternoon and evening as a cold front passes through.

Chances for shower and storms will be higher Sunday afternoon and
evening than it was today, but still uncertainty about how organized
and strong they will get. The latest guidance favors storms
initiating during peak afternoon heating in the NC mountains and
potentially organizing into linear segments as it moves crosses the
Foothills between 19-22Z and Piedmont between 21-00Z. This scenario
would increase the threat for thunderstorm impacts, including strong
winds, at most terminals. Kept any mention of afternoon storms to
the NC terminals (KAVL, KHKY, and KCLT) where confidence is highest.

Outlook: Quiet conditions expected Monday thru midweek. Valley
fog and low stratus is possible each morning, primarily in the
mountain valleys.

&&

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

&&

$$

JCW/JRK