textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Air Quality Alert for ground level ozone was issued for Davie, Mecklenburg, Gaston, York, and Chester counties for Friday from 10 AM to 8 PM.

KEY MESSAGES

1. Hot and humid conditions linger through the weekend with heat index values ranging from 100 to 106 degrees each afternoon. 2. Coverage of mainly diurnal showers and thunderstorms will increase through weekend as a weak cold front moves through our area.

DISCUSSION

Key message 1: Hot and humid conditions linger through the weekend with heat index values ranging from 100 to 106 degrees each afternoon.

Broad upper ridging will be the dominant synoptic feature impacting the weather across the Southeast and Mid-Atlantic thru the end of the week. The potential to reach Heat Advisory criteria appears a bit higher for the weekend as thickness values support slightly warmer temps, and fcst soundings suggest less dry air aloft. However, there is some potential for a broad plume of smoke from wildfires (well to our north) to spread over our area tomorrow, which could suppress temperatures somewhat. Thus, confidence was not high enough to issue any Heat Advisories for tomorrow at this time. Regardless, individuals should prepare for elevated heat risk over the next few days. Stay hydrated, take frequent breaks in air- conditioned or shaded areas, and never leave children or pets unattended in vehicles.

Falling heights/weakening of the upper ridge should result in slightly cooler temperatures by Sunday, but with lower potential for sfc dewpts to mix out during the afternoon. Nonetheless, the current fcst still has heat index values in the 100 to 103 range across the Piedmont and Upstate. This is followed by a return of more typical heat index values for the first half of next week.

Key message 2: Coverage of mainly diurnal showers and thunderstorms will increase through weekend as a weak cold front moves through our area.

The upper ridge will be the primary driver of our weather pattern the next few days. Slightly less capped/more unstable/more moist conditions are expected tomorrow which should allow for a slight increase in diurnal coverage of convection. However, coverage is expected to be best across the central and southern North Carolina mountains, the South Carolina Upstate, and northeast Georgia. The northern North Carolina mountains, North Carolina foothills, and North Carolina Piedmont should remain mostly dry again tomorrow.

With heights falling across the Eastern CONUS, an increase in convective coverage is expected this weekend as a weak cold front moves into our area. Slightly drier and cooler conditions early next week should result in less shower and thunderstorm coverage each day, although another cold front could enhance coverage by Wednesday.

Where convection does develop, sfc-based CAPE of roughly 2500 J/kg and robust downdraft CAPE of 1000+ J/kg will create the potential for a few strong-to-severe downbursts each day, especially over the weekend.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

At KCLT and elsewhere: TSRA is currently impacting KGSP and KGMU so have a TEMPO for the next hour to account for lingering activity. Dry conditions are noted elsewhere as of 00Z. Any lingering TSRA should dissipate around/shortly after sunset allowing dry conditions to return through Friday morning. With no RA reported at KAVL, thinking mountain valley fog and stratus will not develop at the terminal overnight, especially with winds remaining slightly elevated. TSRA will develop once again Friday afternoon and evening with slightly better coverage expected. Thus, introduced PROB30s for TSRA at KAVL and the SC Upstate terminals. KCLT and KHKY should remain dry again Friday. Winds will remain NW at KAVL through Friday morning, going VRB Friday afternoon/early evening. Winds east of the mountains will gradually turn more NW/N overnight before turning more NE/ENE after daybreak. Winds east of the mountains will then gradually turn more SE/S (with some sites going VRB) late Friday afternoon into early Friday evening.

Outlook: Even better coverage of afternoon/evening SHRA/TSRA is expected this weekend with a few strong to severe storms possible each day during peak heating hours. Low stratus and/or fog will be possible each morning, mainly in the mountain valleys.

CLIMATE

RECORDS FOR 07-16

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 94 1988 69 1930 72 2020 49 1926 1980 1897 1932 KCLT 100 1899 67 1930 76 2020 58 2004 1887 1988 2001 KGSP 101 1887 65 1930 79 1937 57 1888

RECORDS FOR 07-17

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 95 1980 72 1917 77 1887 54 1939 1891 KCLT 100 1986 74 1989 80 1881 62 2004 1887 1896 1903 1886 KGSP 103 1887 76 1930 76 1934 60 1886

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...None. SC...None.