Severe Thunderstorm Warning 67, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
135 PM EDT Mon Jun 29 2026

.WHAT HAS CHANGED...
Updated the aviation discussion for the 18Z TAFs.

&&

.KEY MESSAGES...
1. Another round of scattered showers and thunderstorms is possible
west of I-26 this afternoon and evening, with one or two storms
potentially becoming strong to severe.
2. Heat risk will steadily increase through the week, with heat
indices likely exceeding 100 degrees across much of the Piedmont
and foothills, especially by mid to late week. Daily thunderstorms
will also be possible across the mountains.

&&

.DISCUSSION...
Key message 1: Another round of scattered showers and thunderstorms is
possible west of I-26 this afternoon and evening, with one or two
storms potentially becoming strong to severe.

A stout upper ridge continues to build in across the Deep South into
the Tennessee Valley. On the eastern flank of the ridge, deep-layer
northerly flow is in place over the Southern Appalachians. Low-level
convergence has fostered a plume of deep moisture and locally high 0-
3 km ThetaE air generally along and west of the I-26 corridor. Early
afternoon visible satellite imagery depicts a deepening cumulus
field within this plume of moisture with convective initiation to
follow shortly thereafter. Coverage may remain limited and
predominately scattered, but the environment will be conducive to a
few of these storms potentially becoming strong to severe. SPC
mesoanalysis depicts surface-based CAPE upwards of 4500 J/kg along
with 700-1000 J/kg of DCAPE and modest low-level lapse rates.
Locally damaging winds will be the main threat with any severe
storms along with an outside chance for isolated small hail.
Otherwise, the ongoing heat advisory for Elbert County remains in
effect until 8 PM this evening.

Key message 2: Heat risk will steadily increase through the week, with
heat indices likely exceeding 100 degrees across much of the
Piedmont and foothills, especially by mid to late week. Daily
thunderstorms will also be possible across the mountains.

The synoptic pattern will continue to amplify through the week as a
deep trough digs down the west coast while a highly anomalous upper
ridge builds from the Tennessee Valley into the Southern
Appalachians. 500mb heights and 850mb temperatures will both be in
the 99th percentile for the end of June and early July and will
support a building heat wave as we head into the 4th of July holiday
weekend. Temperatures will climb into the mid to upper 90s by
Wednesday with upper 90s to low 100s common east of the mountains
Thursday through the weekend. Mountain valleys will likely see highs
in the low to mid 90s with mid to upper 80s even across the highest
elevations.

The biggest question is whether heat indices reach advisory criteria
of 105 degrees. Historically, for temperatures in the western
Carolinas and northeast Georgia to reach the low 100s we need
relatively dry soil along with dry air. Given ongoing drought
conditions and only scattered swaths of rainfall the last several
days these conditions would appear to be met. Diving deeper into
forecast soundings, and guidance indicates a very deep and well
mixed boundary layer with mixing as deep as 700 mb on the hottest
days this weekend. This in turn results in dewpoints mixing out into
the low 60s and perhaps even the upper 50s. This has major
implications on the heat index forecast with values struggling to
reach criteria despite air temperatures in the low 100s.
Furthermore, you can never rule out a ridge riding upstream
convective complex in these setups. Even if no rain makes it into
the area convective debris clouds could wreak havoc on daytime
temperatures. That being said, while confidence in reaching advisory
criteria is moderate at best, it will still be hot and heat related
stress leading up to and through the holiday weekend needs to be
taken seriously. Those with outdoor plans, including holiday and
recreation, should prepare for several days of elevated heat risk.
Stay hydrated, take frequent breaks in air-conditioned or shaded
areas, and never leave children or pets unattended in vehicles.

In addition to heat, daily afternoon thunderstorms will be possible
across the mountains where topographical influences should help to
initiate at least isolated to widely scattered storms each day. Most
of this activity should remain confined to the mountains, at least
through much of this week. As with any summer storms, a few could
become strong to severe. There are some indications that the pattern
could become more convectively active late weekend and beyond as the
upper ridge breaks down and northwest flow with embedded shortwaves
returns.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Predominately VFR conditions will prevail at
most terminals through the TAF period. An afternoon cumulus field
has developed across the area along with scattered showers and
thunderstorms, mainly along and west of I-26. As such, PROB30 groups
have been carried at KAVL, KGSP, KGMU and KAND for scattered
thunderstorms through this afternoon. Thereafter, any showers and
storms should dissipate through the evening with quiet conditions
overnight and tomorrow morning. The only other thing to watch for
will be the potential for another round of valley fog/stratus at
KAVL, but confidence is too low to warrant mention in the TAF at
this time.

Outlook: Diurnal showers and thunderstorms are expected mainly
across the mountains through the workweek. Mountain valley fog/low
stratus will be possible each morning.

&&

.CLIMATE...
RECORDS FOR 07-02

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      93 1970     65 1943     70 2018     44 1988
                1954
                1931
   KCLT     101 1931     64 1943     76 1991     56 2008
                                        1970
                                        1931
   KGSP     101 1954     66 1943     77 1931     53 1899

RECORDS FOR 07-03

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      93 1970     65 1988     70 2018     50 2008
                1897                    1931        1937
                                                    1932
   KCLT      99 1931     70 1988     76 1925     56 2010
   KGSP      99 2016     70 1988     77 1925     56 1984
                1970
                1953

RECORDS FOR 07-04

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      97 1948     68 1976     70 2016     51 1986
   KCLT      99 1993     70 1968     76 1993     55 1933
                1955
   KGSP     100 1993     70 1988     75 2018     58 2021
                                                    1996
                                                    1933

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory until 8 PM EDT this evening for GAZ029.
NC...None.
SC...None.

&&

TW

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