textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Heat Advisory issued for Saturday

Aviation forecast was for the 18Z TAF issuance.

KEY MESSAGES

1. Heat Advisory in effect for most of the Upstate, NE GA, and the Charlotte Metro area this afternoon and Saturday afternoon. Hot and humid weather continues into next week, with triple digit heat index values expected over the low terrain each afternoon. 2. Scattered diurnal showers and thunderstorms develop each afternoon into early next week. Some strong to severe storms, as well as isolated nuisance flooding, will be possible each day.

DISCUSSION

Key message 1: Heat Advisory in effect for most of the Upstate, NE GA, and the Charlotte Metro area this afternoon and Saturday afternoon. Hot and humid weather continues into next week, with triple digit heat index values expected over the low terrain each afternoon.

The upper anticyclone is forecast to remain to our west but still close enough for high heights and thickness values to remain in place over our area through much of the period. This keeps well above normal high temperatures, but short of records, across the area. Elevated dewpoints will be seen each afternoon allowing heat index values to rise above 105 along and south of the I-85 corridor. Spotty locations across the I-40 corridor could briefly reach 105 as well. Additional Heat Advisories are likely through the period. The guidance highs and dewpoints continue to waffle keeping confidence low that any location will see heat index values reach 110. That said, it will be possible over the Lakelands, so will continue to monitor.

A Heat Advisory remains in effect for today for most of the SC Upstate, NE GA, and the Charlotte Metro area and has been issued for the same locations for Saturday.

Key message 2: Scattered diurnal showers and thunderstorms develop each afternoon into early next week. Some strong to severe storms, as well as isolated nuisance flooding, will be possible each day.

With upper ridging to our west, MCVs from overnight MCSs will continue to track over our area through the weekend. This keeps scattered diurnal convection over the area with Saturday having a higher probability due to a weak surface boundary dropping toward the area. The boundary and the MCV track moves back north next week bringing more typical diurnal convective chances. The very unstable air mass along with steep lapse rates and DCAPE keeps the threat of strong to severe storms over the area as well. Chances higher on Saturday with more organization from the frontal boundary. Isolated flooding also possible with high PW values and slow moving storms.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

At KCLT and elsewhere: Convection already ongoing across the mountains. Have TEMPO for KAVL and KHKY where impacts will be felt first. Have PROB30s for the other sites as convection is expected to spread out of the mountains, but direct impacts are still uncertain. Convection ends by early evening. Expect more convective debris moving in from the NW which should limit fog chances for all but the usually more foggy Little TN Valley, so just VFR in the TAFs for now. Convection returns Saturday afternoon. Light westerly winds, NNW at KAVL, this afternoon becomes calm overnight then N to NW for Saturday.

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 11 AM to 8 PM EDT Saturday for GAZ018-026- 028-029. NC...Heat Advisory until 8 PM EDT this evening for NCZ070>072-082. Heat Advisory from 11 AM to 8 PM EDT Saturday for NCZ070>072- 082. SC...Heat Advisory until 8 PM EDT this evening for SCZ008>014-019- 104>109. Heat Advisory from 11 AM to 8 PM EDT Saturday for SCZ008>014- 019-104>109.