textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

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

KEY MESSAGES

1. Dry weather with comfortable humidity levels will continue through Tuesday. Then humidity increases along with daily shower and thunderstorm chances returning Wednesday and continuing through the rest of the week.

DISCUSSION

Key message 1: Dry weather with comfortable humidity levels will continue through Tuesday. Then humidity increases along with daily shower and thunderstorm chances returning Wednesday and continuing through the rest of the week.

The upper pattern currently consists of a large anticyclone over New Mexico and an upper low over the eastern Great Lakes. Dry sfc high pressure will continue to nose in under the NWLY flow between these features today. The upper low will begin to shift east, allowing flow across the Southeast to flatten out Tuesday. No appreciable change in the air mass is expected thru Tuesday, with dewpts mixing out into the 50s to lower 60s under sunny or mostly sunny skies. No mentionable PoPs in the forecast thru Tuesday. Highs will be near normal. Overnight lows will be slightly below normal, given the lower dewpts and good radiational cooling conditions.

A shortwave trough will dig into the Midwest on Wednesday and back the low- and mid-level flow out of the SW. A warm front will activate across the Deep South and start lifting northward, pushing into the forecast area by early Wednesday evening. This will likely trigger convection, as guidance is in good agreement on dewpts in the mid 60s to lower 70s along/south of the boundary, with at least 1000-2000 J/kg of sbCAPE. So expect a return of showers and thunderstorms in the late aftn and evening, roughly from south to north across the forecast area. Convection may linger well into the night, if there is enough instability along the advancing front.

The upper trough reaches its highest amplitude on Thursday, with its axis still just west of the Appalachians. This will likely result in continued moist SWLY flow and an active convective day Thursday. There is some uncertainty on when the peak activity will occur, as widespread cloud cover may delay destabilization until later in the day. The NBM still has likely PoPs across the Piedmont and categorical PoPs in the mountains. From there, the pattern starts to flatten out again, but lingering upper-level troughiness is shown in the guidance over the eastern CONUS thru the weekend. So, expect typical diurnal PoPs to continue each day thru the end of the period. Other than Thursday, with the cloud cover and precip coverage, holding temps down, temps will be near to slightly above normal, with some guidance trending toward hotter conditions possibly returning Sunday into Monday.

AVIATION /12Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: VFR expected across the area thru the period, except for some mountain valley fog early this morning, but now looks to avoid KAVL. Some cirrus lingers through the day with periods of areas of high-based Cu. Light wind across the Piedmont sites, and rather VRB, favoring a N/NW direction for most of the period, but toggling to W this aftn in the Upstate and at KHKY. N winds pick up with a few low-end gusts possible at KAVL late aftn. Guidance is not showing much fog potential at KAVL tonight, so will leave out any mention with the 12z TAF.

Outlook: No significant chance of convection until Wednesday with an even better chance Thursday into Friday. Mountain valley fog and low stratus is possible each morning.

GSP WATCHES/WARNINGS/ADVISORIES

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