textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 12z TAFs.

KEY MESSAGES

1. Hot and humid conditions linger through the weekend with heat index values ranging from 100 to 105 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 105 degrees each afternoon.

Broad upper ridging over the area today will slowly weaken through the weekend as moves into the Mid-Atlantic by Sunday. Hot and humid conditions are expected today with temperatures slowly dropping into Sunday with lower thickness values. There is some potential for a broad plume of smoke from wildfires (well to our north) to spread over our area today, which could suppress temperatures somewhat. While highs will reach the mid to upper 90s outside of the mountains, the dewpoints remain the question. Latest guidance suggests lower dewpoints with deep mixing today. Therefore, the probability of large areas with a heat index of 105 or higher is low. Therefore, confidence is too low for a Heat Advisory at this time. Still, heat index values will likely be 100 or higher outside of the mountains, so 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.

Even with temperatures falling into the lower 90s by Sunday, dewpoints have less of a chance of mixing out. Therefore, heat index values will likely remain above 100 Saturday and Sunday. 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.

With the upper ridge over the area today, the atmosphere remains relatively capped with high LFC's over the NC Piedmont and eastern Upstate. Conditions will be better across the mountains and slightly better over the western Upstate and NE Georgia. A few of the storms could become severe with damaging winds the main threat.

With heights falling across the Eastern CONUS through the weekend, a cold front moves into the area by Sunday. Expect increasing instability, moisture, and shear. This, along with the potential for some organization, will lead to increasing chances of severe storms Saturday, with the best chance on Sunday, especially over the I-77 corridor. Damaging winds remain the main threat.

After a decrease in convective chances behind the front, especially on Tuesday, the chance picks back up Wednesday as another front moves into the area.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

At KCLT and elsewhere: Mountain valley fog/stratus looks to miss KAVL this morning. Cirrus continues through the day with VFR Cu developing. TSRA expected once again during the afternoon and early evening with slightly better coverage expected. Have retained the PROB30s for TSRA at KAVL and the SC Upstate terminals. KCLT and KHKY should remain dry again. Winds turn more northeasterly during the morning, NNW at KAVL, then turns southerly for the afternoon for all but KAVL where it remains NW. Winds go light and variable during the evening. Mainly cirrus overnight, but mountain valley fog/stratus expected once again.

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. Coverage then diminishes early next week. Low stratus and/or fog will be possible each morning, mainly in the mountain valleys.

CLIMATE

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.