200 FXUS62 KGSP 290642 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 242 AM EDT Mon Jun 29 2026 .WHAT HAS CHANGED... Updated the aviation discussion for the 06Z TAFs. && .KEY MESSAGES... 1. Lingering showers and thunderstorms overnight, mainly west of I-26, with mountain valley fog possible by daybreak. Another round of showers and thunderstorms west of I-26 possible this afternoon and evening, with one or two storms potentially becoming strong to severe. 2. Heat risk will steadily increase through this week, with heat indices likely exceeding 100 degrees across much of the Piedmont and foothills, especially by mid to late week. && .DISCUSSION... Key message 1: Lingering showers and thunderstorms overnight, mainly west of I-26, with mountain valley fog possible by daybreak. Another round of showers and thunderstorms west of I-26 possible this afternoon and evening, with one or two storms potentially becoming strong to severe. A few showers and thunderstorms have moved across the Smokies and southwest mountains of NC. CAMs have hinted at this activity continuing to push further south into portions of the western Upstate and northeast Georgia. Not expecting any of the convection to become strong to severe with the lost of diurnal instability, but will be heavy rainfall producers which could lead to localized ponding on roadways and a sudden rise in creeks and streams. However, the hydro threat is very low as the overall storm motion is fast enough to keep the heavy rainfall moving. Very saturated low-levels and locations that received appreciable rainfall yesterday should promote fog/low stratus development. Confidence is low as to whether or not any dense fog forms, but will need to monitor through the overnight period. Continued northwest flow aloft thanks to a deepening upper-level ridge to the west and the presence of a weak frontal boundary draped along the I-26 corridor, isolated convective initiation is possible during peak heating west of I-26. CAMs vary as far as coverage and intensity, but deep moisture (PWAT >1.50"), sufficient SBCAPE (2000-3000 J/kg), and 20-30 kts of 0-6 km bulk shear on the west side of the boundary suggests that the environment could be enough to support loosely organized convection capable of a strong to severe thunderstorm or two, producing damaging winds. Guidance continues to pinpoint the western Upstate as having the highest probability of a severe storm, but can't be ruled out elsewhere west of I-26. Afternoon highs are forecast to run a category or so above normal, with the southern tier of the CWFA potentially exceeding 100 degree heat indices before any afternoon convection arrives. Key message 2: Heat risk will steadily increase through this week, with heat indices likely exceeding 100 degrees across much of the Piedmont and foothills, especially by mid to late week. An upper-level ridge will strengthen across the eastern CONUS this week, bringing a steady warming trend and suppressing convective coverage. High temperatures are expected to climb into the lower to mid 90s east of the mountains today and Tuesday, with values running 5-10 degrees above normal by mid to late week and the Independence Day Holiday Weekend. Heat index values may approach or exceed 100 degrees starting today through Wednesday, with possible Heat Advisory criteria by Thursday into the holiday weekend. Confidence in exact heat values remain somewhat limited due to uncertainty in afternoon dewpoints potentially mixing out with notable subsidence in the vertical column as heat index values are highly sensitive to dewpoint values. With the ridge in place, convective coverage will be reduced as most activity becomes isolated to scattered and stays mostly confined to mountains during each afternoon and evening, with very isolated instances of convection east of the mountains. Current guidance suggests the synoptic pattern causing the potential prolonged heat could persist through the holiday weekend with little indication of significant relief. While Heat Index for the next couple of days is forecast to be at least several degrees below Advisory criteria, values of around or slightly below 105 are expected to creep into Elbert County, Georgia this afternoon. In collaboration with NWS FFC, Elbert Co will be included in a Heat Advisory. Heat Advisories are likely to continue through the week, while gradually expanding in coverage. 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. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... At KCLT and elsewhere: Mostly VFR conditions expected through the forecast period outside of potential mountain valley fog/low stratus and associated restrictions with any showers and thunderstorms that develop. Kept the MVFR vsby and IFR cig TEMPO mention at KAVL from 08Z through 12Z, while removing any mention of fog/low stratus elsewhere as confidence is too low for a TAF mention. Winds are generally light and variable through daybreak and pick up out of the northeast during the daytime period, while KAVL maintains a north to northwesterly component through the period, with possible low-end gusts (18-22 kts) during peak heating. Guidance continues to develop showers and thunderstorms over the western half of the area, with the best chance of any shower or thunderstorm mention with associated restrictions remaining over KAND and KAVL. Placed a PROB30 for TSRA at KAND and a VCSH mention at KAVL as a result. Lingering convective debris and afternoon cu will keep low VFR cigs in place during the afternoon, but should scatter by this evening into the overnight hours tonight. 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 from noon today to 8 PM EDT this evening for GAZ029. NC...None. SC...None. && $$ CAC