textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 12z TAFs.

Temperatures and heat indices are trending warmer for the middle of next week.

KEY MESSAGES

1. Shower and thunderstorm chances return by the end of the week and continue thru the weekend. 2. Temperatures trend warmer through the weekend and into next week, with triple digit heat indices possible across most of our lower terrain.

DISCUSSION

Key message 1: Shower and thunderstorm chances return by the end of the week and continue thru the weekend.

Weak high pressure will linger over the southeast today helping to keep our fcst area mostly dry. On Friday, the area remains under mostly zonal, stagnant flow aloft while the Bermuda high reasserts itself out over the Atlantic and spreads westward. This will advect deeper moisture into the southeast, bringing increased shower and thunderstorm chances each afternoon thru the weekend. The latest model guidance has increased the shower and thunderstorm chances across most of our CWA for Friday. Over the weekend, the higher chances remain mostly over the NC mtns. At this time, severe thunderstorms are not expected.

Key message 2: Temperatures trend warmer through the weekend and into next week, with triple digit heat indices possible across most of our lower terrain.

The synoptic pattern is looking more favorable for warmer tempera- tures and higher dewpoints, especially by the middle of next week. This increases the chances for 100+ degree heat indices across por- tions of our fcst area. The latest long-range guidance continues to spread stout upper ridging further east and over our region during the first half of next week. As this ridge moves eastward and high pressure builds over the southeast, temperatures will climb. We still expect temperatures on Saturday and Sunday to reach the mid 90s across much of our lower terrain, with upper 90s possible over portions of the Piedmont. These temperatures along with higher dewpoints will likely produce heat index values of 100 to 103 degrees each afternoon for areas along and east of I-77 and areas south of I-85. As the ridge spreads further east early next week, heat indices may top out even higher, especially by the middle of next week. Although the exact values will likely change a bit as we go forward, our confidence is increasing that a good portion of our non-mtn zones will see 100+ degree heat indices by the mid-week. Furthermore, portions of our CWA could see Advisory level heat indices of 105 degrees. This level of heat affects anyone without effective cooling or adequate hydration. If you are outdoors be sure to properly hydrate, wear light clothing, and take frequent breaks to avoid overheating.

AVIATION /12Z THURSDAY THROUGH MONDAY/

At KCLT and elsewhere: Expect dry, VFR conditions to continue thru the 12z TAF period with bkn cirrus this morning giving way to few/sct VFR clouds for the rest of the period. Mtn valley fog has settled over the usual areas, but should not reach KAVL this morning. Otherwise, weak sfc high pressure will linger over the area this morning and continue to weaken thru the day. At the same time, the Bermuda High will begin to reassert itself and winds will pick up from SW this afternoon. They will go light and VRB to calm later this evening.

Outlook: Shower and thunderstorm chances and associated re- strictions increase again Friday onward, especially over the NC mtns.

GSP WATCHES/WARNINGS/ADVISORIES

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