textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Temperatures are trending warmer for the weekend and early next week.

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 may develop this morning across our western zones as deeper moisture spreads over the area from the west. Any thunder/lightning appears unlikely thru the morning as the soundings show too much convective inhibition/negative buoyancy across our area. Better shower and thunderstorm chances return this afternoon and evening as a line of storms develops ahead of an approaching cold front. The latest high-res model guidance continues to depict 20 to 30 kts of deep-layer shear ahead of the front and 1500 to 2500 J/kg of sfc-based CAPE developing during peak heating today. Thus, strong to severe storms are possible. The main hazard still appears to be damaging straight-line winds from any stronger storms. The latest near-term guidance still has the main line/cluster of convection moving through our fcst area from roughly 4 PM to midnight, however the amount of convective coverage remains unclear. Some model guidance shows far more iso- lated to scattered coverage than others. In addition, scattered showers and storms may develop ahead of the main line across the NC Foothills and Piedmont this afternoon allowing for the severe threat to develop a bit earlier. Although SPC's current Slight Risk area covers nearly all of our CWA, confidence regarding the severe threat east of the mtns remains lower because activity is not expected to move east of the mtns until after peak heating today. Thus, damaging winds still appear more likely across the NC mtns and along and north of I-40 where more activity is expected to develop during peak heating hrs. In addition, breezy SWLY winds are also expected ahead of the front today, especially east of the mtns where 20 to 30 mph gusts are expected. Any lingering thunder- storm activity should move east of our CWA shortly after midnight, however most of the near-term guidance brings additional showers over the NC mtns behind the front overnight and into Tues morning.

As the front appears hesitant to completely exit our area on Tues, sct showers and thunderstorms may develop again Tues aftn/early evening along the front (mainly across the SC Upstate), but confi- dence is still fairly low. PoPs remain in the 20 to 30% range during this time window.

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.

Sfc high pressure builds over our region Tuesday into Wednesday allowing brief drying across our area and no significant precip chances on Wednesday. Diurnal shower and thunderstorm chances return by Thursday as another cold front approaches our area from the NW and increasingly moist, SLY flow persists. Diurnal convec- tive chances will continue for the remainder of the week and into the weekend, with temperatures expected to warm each day. There's a decent chance that we will see high temperatures back in the low to mid 90s by Sunday with heat indices exceeding 100 degrees over our southern and southeastern zones.

AVIATION /07Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Expect dry, VFR conditions to continue at all terminals thru the morning. Few to sct high clouds and light to calm winds overnight will pick up again from the SW by late morning. Ahead of an approaching cold front, winds strengthen east of the mountains by the early afternoon with gusts of 15 to 25 kts expected. TSRA chances also increase during the afternoon as some amount of pre-frontal convection is expected to materialize over our area. It remains unclear how much convective coverage we should expect thru the aftn and evening, with the CAM guidance varying considerably from run to run. It also remains unclear how late the thunderstorms will linger, and whether or not the activity along the front itself early Tuesday will be mostly just showers. Nonetheless, it does appear that the NC mtns will see the best convective coverage, so I have prevailing -TSRA at KAVL beginning around 18z today with VCTS this evening for any lingering convection at KAVL. For KHKY, I have a TEMPO for TSRA from 19 to 23z with VCTS after that. For KCLT and the Upstate terminals, PoPs are lower overall and confidence wrt timing is lower, so I kept PROB30s for TSRA from roughly 18 to 24z today with VCTS for any lingering activity.

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.