textproduct: Columbia

WHAT HAS CHANGED

Updated discussion to focus now more on Sunday. Aviation Discussion updated for 00z TAFs.

KEY MESSAGES

- 1. Above normal temperatures through the weekend will increase the risk of heat-related illness.

- 2. Thunderstorm chances are forecast to increase over the next couple of days, with unsettled weather potentially continuing into next week.

DISCUSSION

Key Message 1: Above normal temperatures through the weekend will increase the risk of heat-related illness.

Above normal temperatures will persist across the region again on Sunday as an upper-level ridge remains over the southeast. The ridge is expected to gradually weaken over the next several days as troughing advances eastward. 850-mb temperatures are forecast near the 90th percentile Sunday ahead of an approaching front. Heat indices values on Sunday are forecast to range between 100F-105F once again. Despite the heat, the airmass is not particularly moisture-rich, allowing dewpoints to mix out in the afternoon. This should prevent widespread heat index values from exceeding 108F (our Heat Advisory criteria). Additionally, increasing chances for afternoon/evening convection Sunday during peak heating should help limit max temps and reduce the duration of the most intense heat.

It should be noted that experimental Heat Risk is highlighting major to localized extreme heat impacts across most of the FA again for Sunday. This is likely due to it being early in the summer with temps a few degrees above normal and warm overnight lows. Even though heat indices are expected to stay below advisory criteria, please be sure to take proper precautions. A cooling trend is expected to develop early next week as the ridge begins to break down.

Key Message 2: Thunderstorm chances are forecast to increase over the next couple of days, with unsettled weather potentially continuing into next week.

For Sunday, the environment appears somewhat more favorable for organized convection, with improved forcing and increased shear. 0-6 km bulk shear values of 20-30 kt, combined with increased instability could support a few strong thunderstorms. Storm mode is expected to consist of a few linear segments and multicell clusters ahead of the front, with damaging wind gusts as the primary threat mainly in the late afternoon and into the evening hours. Beyond this weekend, persistently high IVT (90th percentile per NAEFS) should aid in keeping things unsettled early and mid week. By the end end of this upcoming week, it appears that another front may make it into the area & another focus for showers and storms.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Outside of an isolated storm or two, VFR conditions likely through the TAF period.

Generally light W to NW winds of 5-7 kts are being noted across the terminals at this time. A boundary moving toward CAE and CUB within the next 20-40 minutes will likely cause a brief shift to more easterly. As the sun continues to set, winds are expected to become light and variable to calm overnight. Winds increase from the southwest, gusting to 15-20 kts at times after about 15z. As far as precipitation goes, the threat has diminished for tonight and nothing is expected at the terminals. Some isolated to scattered showers/storms are anticipated again Sunday afternoon, but confidence is too low that the terminals will be affected at this time to include in the TAF at this time. The threat for fog is also low due to increasing low level winds and high clouds moving over the area tonight.

EXTENDED AVIATION OUTLOOK...Greater rain chances are expected early next week along with possible associated restrictions.

CAE WATCHES/WARNINGS/ADVISORIES

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