textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Another Heat Advisory issued for Sunday.

Aviation forecast was updated for the 18Z TAF issuance.

KEY MESSAGES

1. Heat Advisory remains in effect for this afternoon, covering most of northeast Georgia and the South Carolina Upstate as well as the Charlotte Metro area. Another Heat Advisory issued for the same area on 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: Heat Advisory remains in effect for this afternoon, covering most of northeast Georgia and the South Carolina Upstate as well as the Charlotte Metro area. Another Heat Advisory issued for the same area on 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 locations as this afternoon's advisory. Expect another one will be needed for Monday and possibly Tuesday.

A Heat Advisory has been issued for most of the SC Upstate and northern Georgia (excluding only the mountainous terrain near the NC state line) as well as the Charlotte Metro area, valid 11 AM thru 8 PM Saturday.

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 /18Z SATURDAY THROUGH THURSDAY/

At KCLT and elsewhere: Convection ongoing near KAVL and KHKY. Have TEMPOs there for TSRA and PROB30s elsewhere. All beginning now except for 19Z at KCLT. Convection diminishes by evening with generally VFR conditions. That said, mountain valley fog is likely but uncertain if it will reach KAVL. Have gone with 6SM and SCT005 to show the potential. Can't rule out restrictions at KHKY but chance too low for the TAF. Overall chance of convection is lower on Sunday, so haven't included it at KCLT yet, although it may be needed at some point. Light and variable winds, low end gusty NNW at KAVL, this afternoon become near calm overnight. Light westerly wind, NNW at KAVL, expected on Sunday.

Outlook: Scattered showers and thunderstorms possible each afternoon with flight restrictions possible for low stratus and fog each morning, especially in the mountain valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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