textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Heat indices are trending slightly warmer for the end of the week.

Updated the aviation discussion for the 06z TAFs.

KEY MESSAGES

1. Showers and thunderstorms possible today and through this evening, with a few becoming severe. Daily thunderstorms are also possible each afternoon through the end of the week. 2. Heat builds by late week into the weekend with triple digit heat indices returning.

DISCUSSION

Key message 1: Showers and thunderstorms possible today and through this evening, with a few becoming severe. Daily thunderstorms are also possible each afternoon through the end of the week.

Another round of thunderstorms are possible today as the CWA remains downstream of the ridge out west. The severity of these storms is highly dependent on how worked over the environment is from previous rounds of showers and thunderstorms. At this time, model guidance, for what its worth, shows an environment with decent instability (if it can recover) and DCAPE by the early afternoon. But this does not take into account cloud debris and how much the air can recover. If it can recover, there is a Marginal Risk (1 out of 5) that a storm could become strong or severe as any remnant MCS makes its way downstream. This is especially the focus for the mountains. Confidence is low to medium on how or where these potential rounds of thunderstorms could occur. As for the remainder of the week, the ridge starts to shift eastward and shuts off the MCS conveyer belt. Given the open warm sector remaining through the end of the week, daily chances for more typical summertime showers and thunderstorms are likely. The higher chances are as usual, over the mountains, with a few pop up showers possible outside the mountains. Chances increase over the weekend for a similar situation.

Key message 2: Heat builds by late week into the weekend with triple digit heat indices returning.

By Thursday and Friday, the ridge makes its way over the southeast and high pressure continues to build. With these height rises returning, so does the hotter temperatures. Current guidance shows mid to upper 90s for most locations east of the mountains on Thursday and Friday. Given the moisture still hanging around, dewpoints are also elevated, which means heat index values of 100- 103 outside the mountains. Friday could be the hotter of the two days with heat index values of 101-105+ in a few locations in the southern zones and NC Piedmont. Confidence is increasing on these hotter heat index values but still room for change. If the axis of the ridge slows down, it could lessen how much the heights rises, affecting the temps. Should the trend for these hotter heat index values continue, there may be a need for a Heat Advisory in the southern counties. There may be a small boundary that comes through over the weekend to slightly cool things down, but confidence is low. Extended guidance shows heat remaining to start the week with triple digit heat index values possible.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

At KCLT and elsewhere: Quiet across the fcst area at the moment, with the usual low stratus and fog in the Little TN River valley. That being said, our attention turns to the next batch of convection upstream in eastern KY, which will reach the NC mountains between 1330Z and 14Z if it holds together. This supports the idea that thunderstorms will be more prevalent than shown in some of the guidance, so the PROB30 will be retained at most sites. However, overall coverage is not expected to be as great as yesterday. In theory. Overall, VFR apart from thunderstorms. Wind will be variable between SW and NW depending on outflows.

Outlook: A few showers or thunderstorms possible each afternoon with flight restrictions possible for low stratus and fog each morning.

GSP WATCHES/WARNINGS/ADVISORIES

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