textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Increased PoPs for this evening and overnight.

KEY MESSAGES

1. An approaching cold front will increase shower and thunderstorm chances across the area today through early Tuesday. Severe thunderstorms will be possible this afternoon and evening, with damaging winds being the main hazard. 2. Brief drying develops Wednesday before diurnal shower and thunderstorm chances return for the rest of the week and the weekend. High temperatures outside the mountains are expected to climb into the low to mid 90s over the weekend.

DISCUSSION

Key message 1: An approaching cold front will increase shower and thunderstorm chances across the area today through early Tuesday. Severe thunderstorms will be possible this afternoon and evening, with damaging winds being the main hazard.

Scattered showers have developed already this afternoon, mostly west of I26, and with CAPEs already >2500J/kg across the Upstate and NE GA expect that coverage and intensity will continue to increase this afternoon. RAP CAPE trends show a pretty strong gradient just off the escarpment this afternoon with CAPEs increasing to over 3000. Add to this some weak deep-layer shear as the remnant MCV pushes over the area late this evening and overnight, and strong to severe thunderstorms will be possible across the area, with damaging winds as the main threat. SPC Slight Risk covers just about the entire area with mostly wind concerns though with a sliver of increased hail threat in the NC Piedmont. Timing, however, is very uncertain with multiple rounds of storms possible with CAMs depicting a round moving mostly through the NW NC Piedmont through evening, with a second round moving into WNC late this evening, with possibly some showers moving in overnight. QPF not particularly concerning with at worst 2 or so inches in the mountains, though it will depend on if any of the convection trains. Finally, ahead of the front, the breezy SW winds will continue with potential gusts to 25-30mph.

Cannot rule out some showers or even thunderstorms developing Tuesday afternoon as the front exits across E/SE zones (generally in the area S of I85 and E of I26) but without the upper support of the MCV just expecting general thunder.

Key message 2: Brief drying develops Wednesday before diurnal shower and thunderstorm chances return for the rest of the week and the weekend. High temperatures outside the mountains are expected to climb into the low to mid 90s over the weekend.

Drier conditions and incrementally cooler temperatures are expected Wednesday behind the front, but a weakness develops in the upper flow splitting the upper western Atlantic ridge from the Desert SW ridge, allowing a return of diurnal convection in the latter half of the work week as temperatures begin rising. By the end of the weekend, highs across the Piedmont are progged to be in the mid to upper 90s, with heat indices exceeding 100. Not out of the question that heat products may be needed for portions of the area, depending on how much dewpoints mix out in the afternoons.

AVIATION /18Z MONDAY THROUGH SATURDAY/

At KCLT and elsewhere: SHRA developing across the western portions of the area, and expect that TSRA will increase through the afternoon. Timing is particularly uncertain but have use a combination of PROB30 and TEMPO, with timing later for KCLT than western TAFs, but convection could easily linger into the overnight hours. Have covered this with VCSH for now but may need to adjust through the period. Enough low level moisture that MVFR to IFR deck is expected to spread in around sunrise Tuesday, burning off between 12-14z. SW gusty winds this afternoon will diminish overnight and then shift NW by Tuesday morning, current timing at KCLT is between 14-18z.

Outlook: Expect drier conditions behind the front Tuesday and Wednesday, with diurnal shower and thunderstorm chances increasing again on Thursday and Friday.

GSP WATCHES/WARNINGS/ADVISORIES

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