textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

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

KEY MESSAGES

1. Hot and muggy conditions continue for most of this week. Relief may arrive by next weekend. 2. Dry conditions continue on Tuesday. Isolated showers and a few storms can't be ruled out over the NC mountains each afternoon this week, but coverage and intensity should remain limited.

DISCUSSION

Key message 1: Hot and muggy conditions continue for most of this week. Relief may arrive by next weekend.

A ~596dm upper anticyclone remains centered over the eastern Ozarks, with elevated upper heights and associated subsidence extending well into the Carolinas. Generally clear conditions were observed across the area at the time of this writing. Think that radiative cooling through the coming hours will permit some fog and low stratus development, mainly in the NC mountain valleys, but otherwise expect quiescent conditions for the overnight.

The forecast for the week has not changed much. Strong subtropical ridging is expected to remain established over the Southeast for the entire week, with very little evolution in the synoptic pattern through Friday. Each afternoon will feature dangerous triple-digit heat index values east of the mountains. We don't quite hit Heat Advisory criteria in the forecast for Tuesday, but by Wednesday and Thursday, confidence is increasing that at least some locations will be under the gun.

Long-range ensembles have begun to coalesce around a Saturday-afternoon-to-evening timeframe for a cold front to cross the area. It still looks like it'll put more of a dent in dewpoints than temperatures, but may nonetheless provide some relief from the heat and humidity.

Key message 2: Dry conditions continue on Tuesday. Isolated showers and a few storms can't be ruled out over the NC mountains each afternoon this week, but coverage and intensity should remain limited.

Not much change to the convective forecast for this week; a subsidence air mass should limit any convection to the ridgetops each afternoon and keep lapse rates poor enough that only isolated showers and weak thunderstorms appear likely through Thursday.

Long-range ensembles continue to depict a cold front crossing the area at the end of the week, but have backed off to more of a Saturday afternoon, where previously at least a chunk of LREF members featured a Friday afternoon FROPA. Aloft, it should be accompanied by a compact shortwave dipping down out of the Ohio Valley and crossing the Carolinas Saturday afternoon/evening. This should result in an improved convective environment compared to the rest of this week as lapse rates improve and upper flow improves marginally, so we'll need to continue to monitor this for any potential severe weather. Confidence, of course, remains quite low at this point.

AVIATION /09Z TUESDAY THROUGH SATURDAY/

At KCLT and elsewhere: Mostly clear across the area this morning, with the exception of the mountain valleys, which as expected are socked into patchy fog and low stratus. Still expect restrictions to remain confined to the mountain valleys (and perhaps a few locations in the foothills) and scatter out quickly after daybreak. Mostly clear conditions expected today, with an afternoon cu field but little to no convective potential, even in the mountains. Should any showers develop, they'll likely be isolated to the ridgetops. Winds will start out light and from the N, eventually toggling to the S this afternoon and evening. Mostly clear conditions persist tonight.

Outlook: Isolated to scattered mountain convection expected through Friday, then expanding to all areas for the weekend. Fog and low stratus will be possible each morning, especially in the mountain valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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