textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

SPC expanded the day 2 slight risk across most of the GSP CWA.

Timing of the main line of convection has been pushed back a bit, now occurring a few hours later compared to yesterday.

A few showers and thunderstorms may develop along the cold front Tuesday afternoon and evening across the South Carolina Upstate but confidence is low.

Trending drier for Wednesday.

KEY MESSAGES

1. Dry today before a cold front brings shower and thunderstorm chances back Monday into Tuesday. Severe storms remain possible Monday afternoon into late Monday evening, with damaging winds being the main hazard.

DISCUSSION

Key message 1: Dry today before a cold front brings shower and thunderstorm chances back Monday into Tuesday. Severe storms remain possible Monday afternoon into late Monday evening, with damaging winds being the main hazard.

Dry today with surface high pressure remaining overhead. The 12Z CAMs show the potential for some isolated convection to develop late this afternoon south of I-85 and west of I-26 but keep most of the activity just south and west of the GSP CWA. It will be warmer today and slightly more humid compared to yesterday. Scattered showers and thunderstorms may develop overnight into early Monday morning across the southern North Carolina mountains, northeast Georgia, and the far northwestern South Carolina Upstate. This activity is not expected to be severe and should dissipate by mid-morning.

Better shower and thunderstorm chances return Monday afternoon and evening as a line of storms develops ahead of a cold front. With 12Z High-res guidance depicting 20-25 kts of deep layer shear available ahead of the front and 1,500-2,200+ J/kg of SBCAPE developing during peak heating hours Monday, strong to severe storms are possible. The main hazard still appears to be damaging wind gusts. Latest high-res trends have the main line tracking a bit slower, with timing for severe storms now looking to be ~4 PM to midnight. Scattered showers and thunderstorms may develop ahead of the main line across the North Carolina Foothills and Piedmont Monday afternoon so these locations may see the severe threat develop a bit earlier. Although SPC expanded the the day 2 slight risk across nearly the entire GSP CWA, confidence on the severe threat east of the mountains is low as activity will not push off the mountains until after peak heating and as the 12Z CAMs show activity gradually weakening through the evening as a result. Confidence on the damaging wind risk is higher across the mountains and along and north of I-40 where activity will develop during peak heating hours. Breezy SW winds can also be expected ahead of the front on Monday, especially east of the mountains where gusts will range from 20-30 mph (well below advisory criteria). Any lingering activity will gradually push south and east of the forecast around or shortly after midnight, allowing drier conditions to return for most locations. However, NW flow rain showers may develop along the NC/TN border behind the front Monday night, lingering through at least Tuesday morning.

Scattered showers and thunderstorms may develop again Tuesday afternoon/early evening right along the front (mainly across the South Carolina Upstate) but confidence is low. As a result of this potential, the latest NBM has trended upward slightly compared to the previous forecast regarding PoPs Tuesday afternoon/evening east of the mountains but again confidence is low.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

At KCLT and elsewhere: Dry and VFR through the 18Z TAF period. Wind direction will be mainly S/SW through the period, with stronger wind speeds expected on Monday ahead of the front. Gusts from 18-24+ kts can be expected mainly east of the mountains on Monday. Shower and thunderstorm chances should hold off until after the 18Z TAF period. FEW to SCT cirrus will stream over the terminals through the period, with daytime cu developing each afternoon.

Outlook: Showers and thunderstorm chances, as well as associated restrictions, return ahead of a cold front Monday afternoon into late Monday evening. Drier conditions return late Monday night into Wednesday, but isolated showers and thunderstorms may develop right along the front Tuesday afternoon/evening across the SC Upstate but confidence is low. Daily shower and thunderstorm chances return by Thursday and linger into the weekend.

GSP WATCHES/WARNINGS/ADVISORIES

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