textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 00Z TAF issuance.

KEY MESSAGES

1. Mostly dry through Tuesday before rain chances return middle of next week as a low pressure system approaches out of the west. 2. Highs peak today before much cooler highs return this weekend into early next week as cold air damming develops. Warmer highs return by Thursday as the low pressure system erodes the wedge.

DISCUSSION

Key message 1: Mostly dry through Tuesday before rain chances return middle of next week as a low pressure system approaches out of the west.

A backdoor cold front tracks across the GSP forecast area tonight into early Saturday morning but will mainly lead to an increase in wind speeds, with low-end gusts developing east of the mountains late tonight into Saturday morning. Outside of this, dry high pressure will be the dominate surface feature through early next week as the southern periphery of the high remains extended over the Carolinas. This surface ridge will act to shunt the bulk of the moisture west and south of the GSP forecast area Sunday through Tuesday. However, cannot entirely rule out some brief rain developing across the North Carolina mountains and northeast Georgia Sunday into Monday per the 12Z NAMNest, 12Z GFS, and 12Z NAM. The 00Z Euro also shows some rain developing across these zones, but mainly Sunday into Sunday night. NBM slight chance PoPs across portions of the North Carolina mountains and extreme northeast Georgia look to follow the timing and coverage of the Euro for now.

Better rain chances still look to return by the middle of next week, possibly lingering through early Friday, as a low pressure system approaches out of the west. However, confidence on exact timing remains low with global models still not in great agreement regarding the exact track/evolution of this system.

Key message 2: Highs peak today before much cooler highs return this weekend into early next week as cold air damming develops. Warmer highs return by Thursday as the low pressure system erodes the wedge.

High temperatures peak today, climbing into the upper 70s to lower 80s in the mountain valleys and east of the mountains thanks to an upper ridge over the Southeast. Upper ridging gradually breaks down this weekend as a shortwave tracks across the Carolinas and northern Georgia. Meanwhile, at the surface, high pressure will center itself over the Northeast allowing cold air damming to develop Saturday into Sunday. The breaking down of the ridge combined with the development of cold air damming will allow much cooler high temperatures to return for the weekend. Highs should end up near to just above normal Saturday and near to just below normal Sunday. With no true erosion mechanism to scour out the wedge early next week, cold air damming should remain in locked in place. Thus, cooler highs should linger through at least Monday but may continue into Tuesday. Right now the NBM has above normal high temperatures returning by Tuesday but would not be surprised to see highs trend lower with future updates as the NBM accounts for the lingering wedge. Warmer high temperatures return mid to late week as the aforementioned low pressure system tracks across the region and finally scours out the wedge.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

At KCLT and elsewhere: Dry and VFR through the 00Z TAF period. A backdoor cold front brings increasing overnight into Saturday morning. Low end gusts look likely across for most of the terminals. KHKY and KAVL the exceptions. Outside of the mountains, wind speed increases from the NE behind the front with gusts developing near or shortly after daybreak. KAVL sees light N wind overnight become light SE after daybreak. BKN to occasionally OVC cirrus will continue through the period. Can't rule out some mountain valley fog in the typically more foggy Little TN Valley, but no fog expected at KAVL.

Outlook: Mostly dry and VFR through Tuesday. Cannot entirely rule out restrictions early next week but confidence is low. Otherwise, rain and associated restrictions should return middle of next week. With cloud cover expected this weekend into much of next week, mountain valley fog formation should remain limited.

GSP WATCHES/WARNINGS/ADVISORIES

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