429 FXUS62 KGSP 291735 AFDGSP 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