textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 00Z TAFs.

KEY MESSAGES

1. Daily chances for showers and thunderstorms linger through the weekend. Isolated severe storms capable of producing damaging wind gusts are possible Saturday afternoon/evening. 2. Elevated heat risk by mid-week, with triple digit heat indices possible across most locations east of the mountains.

DISCUSSION

Key message 1: Daily chances for showers and thunderstorms linger through the weekend. Isolated severe storms capable of producing damaging wind gusts are possible Saturday afternoon/evening.

Kicking off the weekend with a mostly zonal flow aloft and a shortwave passing through. A few showers and thunderstorms have developed across the mountains this evening but are quickly weakening as they push east. Dry conditions have returned east of the mountains this evening. Not expecting any lingering activity this evening to become severe.

For the weekend, a similar pattern emerges, but with one caveat. A developing ridge across the central CONUS begins to build, leaving the southeast and portions of the Mid-Atlantic in the path of potential downstream convection. Depending on how quickly this ridge develops and where the axis sets up, will have a direct impact on whether severe thunderstorms develop. Right now Saturday looks to have the best potential for a low-end severe risk. SPC had the entire GSP CWA in a Marginal Risk for isolated severe storms Saturday afternoon/evening. Activity may linger into the overnight hours but confidence is low at this time. Any severe storms that develop will be capable of producing damaging wind gusts. The severe threat appears lower for Sunday.

Key message 2: Elevated heat risk by mid-week, with triple digit heat indices possible across most locations east of the mountains.

As the ridge out west continues to amplify and move eastward, the probability of triple digit heat indices increases. This stout area of high pressure builds in hot summer heat through the weekend and continues to rise into next week. At this time, guidance has a 70- 80% probability of temperatures east of the mountains reaching 95 degrees or higher from Wednesday onward. Given the increase in moisture resulting in elevated dewpoints, this raises concerns for multiple days of heat indices of 100+. The one caveat, especially for the weekend, is any location that has a shower or thunderstorm could cool isolated areas. But, regardless, the signals are there in the guidance for a multi-day heat event, leading up to the 4th of July weekend. For this, it's important to plan for staying cool. Those who are outdoors should hydrate frequently and take breaks if working outside.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

At KCLT and elsewhere: Mostly dry and VFR through the 00Z TAF period outside of TSRA chances across the NC terminals Saturday afternoon/evening. Thus, introduced PROB30s for TSRA and associated restrictions towards the end of the TAF period across the NC terminals. Could not rule out some -SHRA tracking over KHKY early this evening but confidence is low on whether activity will hold together enough to directly impact the terminal. Winds east of the mountains will be mainly S/SW through the period, although KHKY should see mostly calm winds this evening into early Saturday morning. Low-end gusts of 17-20 kts should develop east of the mountains by Saturday afternoon. Winds at KAVL will start out S'ly, going calm later this evening into early Saturday morning before picking up out of the west mid-morning Saturday. Mountain valley fog/low stratus may develop again overnight, mainly across the Little TN Valley. Confidence on fog/stratus reaching KAVL is low.

Outlook: Shower and thunderstorm chances may linger through late Saturday night but confidence is low at this time. Daily chances for showers and thunderstorms, as well as associated restrictions, will linger through early next week. Mountain valley fog/low stratus will possible each morning, especially in the mountain valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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