textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 06Z TAFs.

KEY MESSAGES

1. A few severe storms capable of producing damaging wind gusts are possible this afternoon. 2. Heat risk will steadily increase through next week, with heat indices potentially exceeding 100 degrees across much of the Piedmont and foothills, especially by mid to late week.

DISCUSSION

Key message 1: A few severe storms capable of producing damaging wind gusts are possible this afternoon.

Deepening upper/mid-level anticyclone over the mid/lower MS Valley will help set the stage for potential convection this morning and afternoon. An ongoing MCV over the eastern half of TN will gradually track towards the CWFA later this morning with an initial bout of showers and thunderstorms, mainly across the mountains. CAMs continue to showcase a remnant outflow from this feature that is expected to track southeast and initiate convection downstream into the foothills and Piedmont, but timing and location is still relatively variable. Low-level shear and lapse rates are weaker compared to yesterday, so any storm clustering or organized convection will be limited and thus, keeping the overall severe threat low. However, if convection can initiate into the afternoon and early evening, the convection can tap into better instability, which will uptick the severe threat with the primary hazard being damaging wind gusts. PoPs peak at likely/categorical over the mountains this morning and fall off to chance PoPs across the rest of the CWFA late this morning into the afternoon.

With convective debris set to move across the CWFA earlier than a typical summertime diurnal setup, expect temperatures to be near- normal for late June outside of the southern portions of the CWFA. Dewpoints will be in the upper 60s to low 70s and with the delayed onset of cloud cover across the southern tier, there is a possibility for temperatures to rise into the low to mid 90s, with heat indices approaching triple digits for a few hours during peak heating.

Key message 2: Heat risk will steadily increase through next week, with heat indices potentially 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 next week, bringing a steady warming trend and suppressing convective activity. High temperatures are expected to climb into the lower to mid 90s east of the mountains by midweek, with values running 5-10 degrees above normal by late week and the Independence Day Holiday Weekend.

Heat index values may approach or exceed 100 degrees starting Monday through Wednesday, with possible Heat Advisory criteria by Thursday into the holiday weekend. Confidence in exact heat values remains somewhat limited due to uncertainty in afternoon dewpoints potentially mixing out with notable subsidence in the vertical column. With the ridge in place, convective coverage will be reduced as most activity becomes isolated and stays mostly confined to mountains during each afternoon and evening. Current guidance suggests the synoptic pattern causing the potential prolonged heat could persist through the holiday weekend with little indication of significant relief.

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 /07Z SUNDAY THROUGH THURSDAY/

At KCLT and elsewhere: Some instances of MVFR/IFR fog has developed across the area, but not currently affecting any of the TAF sites. Guidance hinted at this and has highlighted KHKY and KCLT as having the best potential to receive vsby restrictions just before and around daybreak. Included an MVFR vsby mention at both terminals, with a TEMPO for IFR at KHKY through 14Z. Showers and thunderstorms are expected to move across the mountains later this morning, so placed a VCSH mention at KAVL and KHKY, but may need to include a TEMPO or prevailing SHRA line by the 12Z update depending on how the activity over TN trends. This activity is expected to move across the rest of the foothills and Piedmont by late morning into the afternoon. The overall timing and location remains variable, so only placed a PROB30 for TSRA and associated restrictions at the Upstate sites and KCLT. Southwesterly to west-southwesterly winds are expected through the morning and afternoon, with some low-end gusts possible during peak heating. Following the aforementioned showers and thunderstorms, the wind direction is expected to toggle more west-northwesterly to northwesterly behind the activity late in the afternoon and evening. Lingering convective debris will keep mid-level clouds in place, but should scatter out overnight. Depending on how fast the cloud cover disperses overnight, fog and low stratus may develop across portions of the area and possibly impact the terminals by daybreak Monday.

Outlook: Diurnal showers and thunderstorms are expected mainly across the mountains next week. 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...None. NC...None. SC...None.