textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

A Dense Fog Advisory was issued for portions of the NC foothills and NW Piedmont until 9 AM EDT.

The aviation discussion was updated for the upcoming 12Z TAF issuance.

KEY MESSAGES

1. Daily shower and thunderstorm chances continue through the weekend. Locally heavy rainfall and a few strong storms will be possible this afternoon and evening, and again on Friday. 2. A drying and warming trend is expected early next week, with hot temperatures and increased humidity by midweek.

DISCUSSION

Key message 1: Daily shower and thunderstorm chances continue through the weekend. Locally heavy rainfall and a few strong storms will be possible this afternoon and evening, and again on Friday.

Issued a Dense Fog Advisory for most of the NC Foothills and western NW Piedmont until 13z. Fog is already starting to improve in the southern part of the advisory, so it may be canceled early, if the rest of the fog starts lifting as well. The densest part seems to be in the Hickory area.

Otherwise...A series of upper-level shortwaves will dive thru a long wave trough axis and across the CWFA today thru Friday. These will work to deepen the trough and start to swing the axis across the area on Friday. An axis of deep moisture has set up along and east of the Appalachians, which will support elevated precip chances. Scattered to numerous showers and thunderstorms are expected to develop across the mountains this aftn, then coverage shifts east to the Piedmont mainly during the evening hours. Despite starting out with plenty of cloud cover, enough breaking up of the clouds is expected to result in a warm, muggy day. Given the expected higher coverage of activity, and PWATs in the 1.5-2.0" range, isolated, localized heavy rain and nuisance flooding cannot be ruled out. As for severe potential, solid 1000-2000 J/kg of MLCAPE and increasing flow aloft ahead of the upper trough may support a few strong to severe storms today. Similar conditions expected on Friday, with perhaps a little more upper support and bulk shear. The Day 2 SPC Convective Outlook has our area in a marginal risk, which seems reasonable. Damaging wind gusts will be the main threat with the strongest storms. Max temps will be near normal, while lows will be slightly above normal.

Key message 2: A drying and warming trend is expected early next week, with hot temperatures and increased humidity by midweek.

The upper trough begins to fill in, as strong upper ridging across the Southwest/Southern Plains will build east over the weekend, and become centered over the Southeast early next week. Dry air gradually works in from the west, tapering diurnal convection chances to mainly widely scattered in the mountains and isolated in the Piedmont. By Monday, convection will be largely confined to the usual NC mountain ridgetops. Another round of hot, humid weather is looking more likely in the latest medium-range guidance trends. Highs will be back well into the 90s east of the mountains by Tuesday and Wednesday, with heat indices possibly pushing into the 100-105 range across portions of the Upper Savannah Valley and the Charlotte area.

AVIATION /12Z THURSDAY THROUGH MONDAY/

At KCLT and elsewhere: An area of IFR to MVFR stratus has shifted mainly just south of the Upstate TAF sites, while still persisting over KCLT to start the 12z TAF period. Mtn valley fog and areas of fog around KHKY should improve quickly after sunrise. Expect all sites to go VFR by around 16z, with plenty of VFR-level Cu forming this aftn. A little better coverage of convection is expected across the area this aftn into this evening. Overall, expect convection to start in the mtns, then drift east into the Piedmont late aftn thru late evening. Convection should wane overnight. Guidance generally agrees on similar conditions tonight, with areas of IFR to MVFR stratus and patchy fog across the area. Winds will be light thru the period (except possible gusts around thunderstorms), favoring a S to SW direction in the aftn.

Outlook: Good diurnal coverage of SHRA/TSRA Friday and Saturday, with less coverage Sunday and Monday. Mountain valley fog and low stratus is possible each morning.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Dense Fog Advisory until 9 AM EDT this morning for NCZ035-056- 068-069-501>508-510. SC...None.