textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Cooler, possibly significantly cooler, for the middle fo next week.

The aviation discussion was updated to reflect the recent 18Z TAF issuance.

KEY MESSAGES

1. Summer-like weather with hot conditions and afternoon showers and thunderstorms continue through Monday. 2. Precipitation chances continue Tuesday through Thursday with temperatures dropping to near or even below normal.

DISCUSSION

Key message 1: Summer-like weather with hot conditions and afternoon showers and thunderstorms continue through Monday.

Isolated diurnal convection possible across the mountains this afternoon and evening. Otherwise, hot and dry conditions continue. Expect more mountain valley fog overnight.

Upper ridge over the area weakens as shortwaves move across the Mid- Atlantic and an upper low moves west across Florida. This allows shortwaves to move around the periphery of the ridge and across our area Friday. With a moist and unstable air mass in place across the area, expect convection to develop during the afternoon. An outflow boundary from overnight convection will move south into the area as well with the potential to help bring some organization to the convection. Steep low level lapse rates and the weak organization will lead to the potential for isolated damaging wet microburst in the stronger storms, especially from the Blue Ridge south and east across the Piedmont. SPC has this area in a Marginal risk of severe storms which looks reasonable given these factors. Highs will be in the low to mid 90s outside of the mountains and around 90 in the warmer mountain valleys.

A backdoor cold front drops into the area Saturday bringing clouds and cooler but still above normal temps. There will also be an increase in deep moisture. With the forcing and moisture, expect more widespread convection but a lower severe threat. There may be some spotty heavy rainfall, but the overall flood threat is low.

Temperatures tick back up Sunday and Monday as the backdoor cold front dissipates and southerly flow returns. This keeps deep moisture over the area. Quasi-zonal flow will bring some shortwaves moving over the area as well. This keeps a good chance of convection across the area both days. Instability is weak though. Therefore the chance of severe storms is very low. There could be some heavy rainfall on Monday given the coverage of convection. There will be a low flood threat especially after a few straight days with convection.

Key message 2: Precipitation chances continue Tuesday through Thursday with temperatures dropping to near or even below normal.

Fall may finally be on the way by the middle of next week. A cold front drops into the area Tuesday, through the area Wednesday, and south of the area Thursday. The forcing combined with continued deep moisture keeps a good chance of showers and thunderstorms across the area Tuesday. Highs will drop to near normal. Guidance agrees on a cooler and drier airmass moving in behind the front Wednesday and Thursday. There may be enough lingering moisture to keep some showers over the area both days, but it looks like coverage should be lower than the previous few days. There is a signal for the potential for the high building behind the front to be a Cold Air Damming high. This would lead to much below normal temps developing. This is still uncertain as a drier and less cloudy air mass would keep temps from falling that low. However, do expect at least near normal temps which will be much cooler than recent conditions.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

At KCLT and elsewhere: FEW to SCT VFR Cu this afternoon with light and variable to light southerly wind, NNW at KAVL. Isolated convection expected across the mountains but chance too low to include in the KAVL TAF at this time. Convective chances and Cu diminish with loss of heating. Another round of mountain valley fog/stratus develops overnight, have MVFR TEMPO LIFR at KAVL. Fog possible at elsewhere, but chance too low to include for now. Northerly wind picks up during the day Friday with developing VFR Cu. A better chance of convection across the area Friday afternoon and evening. Given the timing of this set of TAFs, have only included a PROB30 at KCLT. They may be needed elsewhere for the next TAF set.

Outlook: Chances of showers and thunderstorms with associated restrictions continue through Tuesday. Mountain valley fog and low stratus will be possible each morning. Low clouds are possible all locations Saturday morning.

GSP WATCHES/WARNINGS/ADVISORIES

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