textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

No significant changes to the forecast early this morning.

The aviation forecast was updated for the impending 12Z TAF issuance.

KEY MESSAGES

1. A Heat Advisory is in effect once again for Upstate SC, northeast Georgia, and the Charlotte Metro area for Sunday afternoon. Hot and humid weather continues for most of the week, with triple digit heat index likely over the low terrain each afternoon. 2. Diurnal convection develops each afternoon this week, with a couple of strong to severe storms as well as isolated nuisance flooding possible each day.

DISCUSSION

Key message 1: A Heat Advisory is in effect once again for Upstate SC, northeast Georgia, and the Charlotte Metro area for Sunday afternoon. Hot and humid weather continues for most of the week, with triple digit heat index likely over the low terrain each afternoon.

Stout subtropical ridging remains in place this morning, with the core of a a 599dm h50 anticyclone centered over eastern Texas per the latest RAP UA analysis. This pattern still looks to remain more or less unchanged through the remainder of the weekend and much of next week. The result will be widespread triple-digit heat indices outside the mountains. A heat advisory is in effect from noon through 8 PM Sunday, for most of the SC Upstate, northeast Georgia, and the Charlotte Metro area, where heat index values will creep above 105 degrees during the hottest part of the day. More heat advisories will likely be needed the first half of the week.

Long-range ensembles continue to feature some cooling by the end of the week, though they've backed off on timing until Friday or even next Saturday. Still think there won't be a true air mass change, so much as a weak burst of cooler air. Still, any relief from the heat will be appreciated.

Key message 2: Diurnal convection develops each afternoon this week, with a couple of strong to severe storms as well as isolated nuisance flooding possible each day.

With little change to the air mass - hot and humid, to be exact - we can expect isolated to scattered diurnal thunderstorms each afternoon from Sunday through at least Wednesday. Lapse rates will generally be poor, but rich instability will nonetheless provide a good enough environment to support a couple strong to severe storms each day. Coverage will generally be best over the mountains, where ridgetops will aid in convective initiation.

By Thursday or Friday, a weakness in the subtropical ridge will provide the impetus for a weak cold front approach the area (possibly pushing south across the region on Friday). Depending on timing, this could improve coverage over showers and storms Thursday or Friday afternoon, and suppress convection in its wake.

AVIATION /07Z SUNDAY THROUGH THURSDAY/

At KCLT and elsewhere: Still expect generally clear skies, with increasing cu coverage through early afternoon. Another round of isolated to widely scattered convection will develop in the afternoon. Confidence is limited on how much, if any, of this convection will survive outside the mountains, but opted to add PROB30s at GSP, GMU, and CLT this afternoon. Mostly clear conditions will return Sunday night, and another round of mountain valley fog and low stratus is likely.

Outlook: Scattered showers and thunderstorms with associated flight restrictions will be possible each afternoon thru at least the first half of next week. Low stratus and fog will be possible each morning, especially in the mountain valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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