textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Confidence increasing slightly in heat index values getting into the 100 to 105-degree range across the southern and eastern Piedmont Thursday through Saturday, with 105+ heat indices possible in the Charlotte area Friday.

The aviation discussion has been updated for the 18Z TAFs.

KEY MESSAGES

1. Temperatures warm closer to normal Wednesday, with afternoon showers and thunderstorms confined to far western areas. 2. Hot conditions will return to the area Thursday and continue into the weekend. Heat index values may return into the 100 to 105 degree range across the Piedmont Friday through Sunday. A cold front will approach from the north and bring higher rain chances over the weekend, and slightly cooler temperatures early next week.

DISCUSSION

Key message 1: Temperatures warm closer to normal Wednesday, with afternoon showers and thunderstorms confined to far western areas.

Scattered to numerous showers continue to bubble up across the western half or so of the CWFA, as dry air filters in from the east. While sbCAPE has increased to around 1500-2000 J/kg in the far southern and western areas, but thunder chances look to be isolated, with severe threat being very low. Showers continue to be efficient rain producers, so localized heavy rain is possible.

Overnight, dry air will continue to work in and cut off precip chances and clear out clouds. Sfc high pressure will settle over the area, allowing for light to calm winds and decent radiational cooling. With moist BL from the rainy weather last couple of days will support the development of patchy fog and low stratus. Not expecting widespread dense fog. Lows will be near normal.

The weak sfc high will remain over the area on Wednesday, shunting deeper moisture to our west. A few diurnal showers and isolated tstms will be possible in the far western NC mountains and NE GA counties, but the rest of the area looks dry. Temps will return to near normal under mostly sunny skies.

Key message 2: Hot conditions will return to the area Thursday and continue into the weekend. Heat index values may return into the 100 to 105 degree range across the Piedmont Friday through Sunday. A cold front will approach from the north and bring higher rain chances over the weekend, and slightly cooler temperatures early next week.

An upper ridge will build across the region starting tomorrow and linger through Friday. This will bring above-normal temperatures and elevated heat and humidity. Heat index values may top out over 100 degrees across the southern and eastern Piedmont each day Thursday thru Saturday. Friday may be the hottest day, with much of the Piedmont reaching 100+ peak heat index values, and up to 105 across portions of the Charlotte area and the southern Lakelands. A Heat Advisory may be needed for parts of the area, if these trends hold. Heat will begin to abate slightly Sunday and into early next week, as an upper trough digs across the eastern CONUS and allows a cold front to slide into the area from the north.

PoPs will likely remain below seasonal normals Thursday and Friday across the Piedmont, but with more typical coverage in the high terrain. Then above-climo PoPs will be possible Saturday and Sunday due to the influence of the approaching frontal boundary. Typical pulse severe chances may return with this activity. Despite the latest global models showing continued unsettled weather Monday, the NBM has come in with lower PoPs.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

At KCLT and elsewhere: IFR to MVFR stratus is slowly eroding from east to west across the Carolinas early this aftn, with VFR conditions expected to start out the 18z TAF at KCLT and KHKY, but with some MVFR (and possibly IFR) lingering at the other sites for the first 1-2 hours of the TAF. Within the lower cloud deck, still plenty of embedded SHRA, but should mainly shift west of the Upstate TAF sites by early evening. Due to the moist conditions across the area tonight, patchy fog and potentially a LIFR/IFR stratus deck may develop, especially across the Upstate and in the mountain valleys overnight. Guidance seems to be trending more pessimistic with cigs/vsby overall, so have reflected that in the 18z TAFs. KCLT has the lowest chances of any restrictions, thanks to drier air working in from the NE. But some patchy fog around KCLT near daybreak cannot be ruled out. Will leave out any mention there for now. Whatever fog and/or stratus develops should burn off fairly quickly Wednesday morning, leaving clear to mostly clear skies by late morning across the area. Winds will continue to be NE/ENE across the Piedmont until early evening, then go lgt/vrb at all sites and continue thru the end of the TAF period.

Outlook: Drier conditions are expected Wednesday into Thursday. Typical mid-July coverage of diurnal convection is expected to return Friday and continue thru the weekend. Low stratus and/or fog will be possible each morning, mainly in the mtn valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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