831
FXUS62 KGSP 261727
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
127 PM EDT Thu Jun 26 2025

.SYNOPSIS...
The upper ridge which was responsible for the very hot weather we
have had will gradually weaken, allowing temperatures to get closer
to normal through the weekend. A disturbance meandering over the
Deep South will help produce mainly afternoon and evening showers
and thunderstorms each day.  A weak cold front reaches our region by
Tuesday and becomes stationary west to east through mid week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 928 AM Thursday...

Key Messages:

1) Hot and Humid Again but not as Hot or Humid as the Last Two Days

2) Heat Advisory in Effect from 2PM to 8PM Along the I-77 Corridor

3) Another Round of Strong to Severe Storms Develops this Afternoon
and Evening but Coverage and Intensity Should be Less than Yesterday

A couple stray showers continue to drift across the area with a
couple returns over the mountains and another small shower over
Lincoln County. Overall, the forecast remains dry through the rest
of the morning before another round of diurnally driven storms this
afternoon. No changes were needed with this update.

Weak upper ridging remains over the eastern United States while a
weak upper low lifts northward over Florida through the period. This
will allow the heat and humidity to lower just a bit today (we will
take any relief we can get at this point). Temps this afternoon will
end up ~3-4 degrees cooler compared to yesterday but will still end
up around 5-10 degrees above normal. Highs will range from the low
to mid 90s east of the mountains and the upper 80s to lower 90s
across the mountain valleys. Triple digit heat indices are once
again expected, mainly east of the NC mountains. However, the
Caldwell, Burke, McDowell, Rutherford and Polk mountain zones will
see triple digit heat indices return today. Locations along/near the
I-77 corridor are most likely to reach Heat Advisory criteria this
afternoon/early evening so the Heat Advisory remains in effect from
2pm to 8pm. Heat indices in the advisory will range from 105-108
degrees F. Another round of strong to severe storms can be expected
this afternoon and evening but activity is not expected to be a
robust as what we saw yesterday. Although deep layer shear will
increase slightly, ranging from 10-15 kts, both SBCAPE and DCAPE
will a few hundred J/kg lower than yesterday. SBCAPE should
generally range from 2,000-3,000 J/kg with DCAPE ranging from 900-
1,300 J/kg per the latest high res guidance and model soundings. The
Day 1 SPC Severe Weather Outlook has the entire forecast area in a
Marginal risk for severe storms and this appears warranted based on
the expected environment today. Damaging wind gusts from microbursts
will continue to be the main hazard with any severe storms that
develop but isolated, brief large hail is also possible. The Day 1
WPC Excessive Rainfall Outlook has most of the forecast area in a
Marginal risk so the isolated heavy rainfall/flooding threat will
return again today (especially for areas that saw heavy rainfall
yesterday and that get heavy rainfall again today).

Drier conditions will gradually develop late this evening into
tonight once convection wanes. Lows tonight will be similar to this
morning, ending up around 5-8 degrees above normal. Patchy mountain
valley fog and low stratus should develop again tonight into
daybreak Friday.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 250 AM EDT Thursday: The pattern will remain unsettled with
showers and storms expected again Friday and Saturday. Coverage
should be enhanced with an upper diffluent pattern in between a
weak upper low near FL and a flat trough over the Great Lakes. The
typical mountaintop and lee trough convergence will be the triggers
for convective initiation, and shear and thermal profiles will
support a pulse storm mode. The NBM has categorical PoPs in the
mountains tapering to likely in the Foothills and high-end chc
southeast of I-85. This seems a little high, but over a 12-hour
period, coverage may largely verify these values. A few strong
wet microbursts can be expected both days from mid aftn to early
evening. Also, weak steering flow and elevated PWATs will yield an
isolated/localized heavy rain/flood threat. Temps will continue
to be slightly above normal, with highs in the upper 80s in the
lowest mountain valleys and lower 90s east of the mountains. Lows
in the 60s in the mountains and generally 68-74 east. Dewpts do
not mix out much either day, keeping heat indices elevated and
possibly topping out in the 100-105 deg F range in the southern
Upper Savannah Valley and the Charlotte area. But not expecting
to need a Heat Advisory either day.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 300 AM EDT Thursday: A weak upper low will open up into a
relative weakness in the subtropical ridge over FL/GA Sunday,
while a northern stream trough digs into the Great Lakes and
Ohio Valley. This set up should keep enhanced diurnal convection
going thru the first half of next week. In fact, the deterministic
guidance shows even more convective response Sunday thru Tuesday
than what we`re expecting Friday and Saturday. The digging trough
will bring a weak cold front SE toward the forecast area and may
provide extra convergence for convection Tuesday. Pretty much every
day has similar PoPs and temps, with a slight uptick in PoPs and a
slight downward trend in max temps Tuesday. The above-climo PoPs may
increase excessive rain/flash flood threats as we continue with this
pattern. Sever threat should remain a few wet microbursts each day,
with perhaps an increase in more organized storms Tuesday thanks
to a little more shear and upper divergence associated with the
digging upper trough.

There is disagreement between the GFS and ECMWF on whether the cold
front will push far enough thru the forecast area to dry us out
and bring temps back to normal. The GFS hangs the front up across
the Piedmont, while the EC pushes it to the I-20 corridor. It`s
difficult for a front to clear thru the area this time of year,
and the EC seems to be on the more amplified side of the LREF
guidance on the 500 mb trough. So while PoPs are lower, they are
still elevated for Wednesday (50-70%).

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
At KCLT and elsewhere: VFR conditions are ongoing at most terminals
early this afternoon but another round of afternoon showers and
thunderstorms is already underway. Temporary restrictions from
thunderstorms will be possible at KAVL and KHKY over the next
several hours. Activity may spread farther east through the rest of
the afternoon with restrictions possible along the I-85 terminals.
Any storms should dissipate this evening with loss of daytime
heating. VFR conditions will prevail overnight with the exception of
any patchy fog, especially in mountain valleys. Confidence is too
low to warrant mention in any TAFs at this point. Another batch of
afternoon storms will be possible again tomorrow.

Outlook: Daily chances for afternoon and evening showers and
thunderstorms continue into next week. Fog and/or low stratus will
be possible each morning in the usual mountain valleys as well as
near lakes and rivers.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Heat Advisory until 8 PM EDT this evening for NCZ036-037-057-
     071-072-082.
SC...None.

&&

$$

SYNOPSIS...ARK
NEAR TERM...AR/TW
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...TW