textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 12Z TAFs.

KEY MESSAGES

1. Elevated heat index values continue through Wednesday. Cooler temperatures later in the week should provide some relief from the heat. 2. Another round of scattered convection with a few severe storms possible today. Less convective coverage is anticipated on Tuesday, but a few severe storms remain possible. A weak cold front brings increased coverage and the potential for more severe weather on Wednesday.

DISCUSSION

Key message 1: Elevated heat index values continue through Wednesday. Cooler temperatures later in the week should provide some relief from the heat.

Highs remain nearly steady in the low to mid 90s outside of the mountains today and Tuesday. Dewpoints should mix out enough to keep heat index values below 105 for most locations. That said, can't rule out a spotty brief 105 value along and south of the I-85 corridor either day. Temps do fall a few degrees Wednesday but dewpoints remain elevated. This keeps elevated heat index values along and south of the I-85 corridor. Again, most locations remain below 105 but a spotty brief 105 is possible. An airmass change takes place behind a cold front for Thursday and Friday. Highs actually end up below normal, a welcome break from the recent heat and humidity. Until then, stay hydrated, take frequent breaks in air- conditioned or shaded areas, and never leave children or pets unattended in vehicles.

Key message 2: Another round of scattered convection with a few severe storms possible today. Less convective coverage is anticipated on Tuesday, but a few severe storms remain possible. A weak cold front brings increased coverage and the potential for more severe weather on Wednesday.

A weak frontal boundary stalls over NC today. The convergence along the front will keep better convective chances over NC. The latest CAMs keep NE GA and the Upstate mostly dry, with chances mainly over the mountains. This looks reasonable given the lower instability and higher LFC's over those areas. Shear is limited today but the air mass over NC is very unstable with high PW values and steep low level lapse rates. This keeps the threat of a few severe storms in place with damaging winds the main threat. Convective coverage for Tuesday is higher across the mountains where better moisture and instability exist with the weak front washing out or moving back northward. The threat of a few severe storms with damaging winds continues. Coverage is expected to increase again on Wednesday as an upper trof amplifies over the eastern CONUS and moves yet another cold front into our area. Severe storm potential may also increase again on Wednesday with the better forcing, moisture convergence, and bulk shear to go along with the unstable airmass. Even with the front moving south of the area, more typical diurnal convection chances return for the end of the week.

AVIATION /12Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Mountain valley fog at KAVL will dissipate this morning. Otherwise, VFR expected outside of convection through the day. With a frontal boundary draped across NC, expect diurnal convection to fire there, so PROB30s in place. The guidance shows less instability and forcing over SC. The CAMs keep convection north of the SC sites, so have removed the PROB30s there for now. Light SW wind picks up during the day then becomes light overnight. Mountain valley fog expected again.

Outlook: SHRA/TSRA may return again Tue though more likely to remain near the NC mountains that afternoon as compared to Monday. Coverage is expected to increase again on Wednesday and Thursday then decrease on Friday. Low stratus and/or fog will be possible each morning, mainly in the mtn valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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