textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The aviation forecast was updated for the 00z TAF issuance.

KEY MESSAGES

1. Another Heat Advisory has been issued for most of NE Georgia, the SC Upstate, and the CLT metro area for Sunday. Hot and humid weather continues into the first part of next week, with triple digit heat index values likely over the low terrain each afternoon. 2. There overall severe threat is lower than previously expected this afternoon but not eliminated. Isolated to scattered diurnal showers and storms develop each afternoon through the middle of next week. A couple of strong to severe storms, as well as isolated nuisance flooding, will be possible each day.

DISCUSSION

Key message 1: Another Heat Advisory has been issued for most of NE Georgia, the SC Upstate, and the CLT metro area for Sunday. Hot and humid weather continues into the first part of next week, with triple digit heat index values likely over the low terrain each afternoon.

The upper anticyclone remains in place to our west through early next week keeping high heights and thicknesses over the area. This means the hot temperatures continue through that time period. With elevated dewpoints continuing through that period as well, heat index values will exceed 100 outside of the mountains through at least Tuesday. Another Heat Advisory has been issued for Sunday for the same loca- tions as this afternoon's Advisory. Expect another one will be needed for Monday and possibly Tuesday.

Although the guidance is showing the anticyclone migrating westward with a steep ridge building over the west coast through the end of the period, heights over our area don't substantially fall until Friday. This keeps the potential for elevated heat index values over the area until then, although the coverage of triple digit values will diminish.

Key message 2: There overall severe threat is lower than previously expected this afternoon but not eliminated. Isolated to scattered diurnal showers and storms develop each afternoon through the middle of next week. A couple of strong to severe storms, as well as isolated nuisance flooding, will be possible each day.

Despite a very unstable air mass, along with steep low level lapse rates and high DCAPE, remain over our area this afternoon. Shear remains weak. The frontal boundary to our north won't move as far south as expected either. This means that there will a lower potential for organized storms. However, given the instability and DCAPE a few severe storms are expected to produce damaging wind gusts. High PW values and slow moving storms could lead to some isolated flooding.

Similar conditions are expected into the middle of next week with isolated to scattered convection, a few severe storms, and possibly isolated flooding.

For the latter part of the week, a developing shallow trough over the eastern CONUS could help push a frontal boundary into the area with better coverage of convection, but details remain uncertain.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

At KCLT and elsewhere: We've still got a few clusters of showers and thunderstorms over the fcst area this evening, with one cell developing very close to KAVL. I have VCTS for KAVL and KHKY until roughly 02z, but after that, connective activity should be mostly done for the evening. Otherwise, expect mostly dry, VFR conditions thru the period with winds becoming calm at most sites later this evening and remaining that way thru tomorrow morning. Winds will eventually pick up from the SW (outside the mtns) tomorrow aftn, with speeds around 5 kts. Some amount of mtn valley fog is likely overnight, but it remains unclear if it will reach KAVL. For now, I have 5SM and SCT003 beginning around 09z. I also have 5SM and SCT005 at KHKY but my confidence is lower there. The chances for convection are lower on Sunday with only KAVL carrying a mention of it at this time with a PROB30 for TSRA. Going forward, if ex- pected coverage trends higher for our area, more sites will likely need PROB30s for Sunday aftn/evening.

Outlook: Scattered showers and thunderstorms and their associated restrictions will be possible each aftn/evening thru early next week. Low stratus and fog will be possible each morning, especially in the mtn valleys.

GSP WATCHES/WARNINGS/ADVISORIES

GA...Heat Advisory from noon to 8 PM EDT Sunday for GAZ018-026-028- 029. NC...Heat Advisory from noon to 8 PM EDT Sunday for NCZ070>072-082. SC...Heat Advisory from noon to 8 PM EDT Sunday for SCZ008>014-019- 104>109.