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KEY MESSAGES

Updated at 111 PM EDT Sat Aug 15 2026

- Dangerous heat continues Sunday and likely into Monday, especially south and central TN Valley where the Heat Index will peak between 105 and 110. - Organized storms near a cold front are expected Monday afternoon and evening and may pose a threat of damaging winds.

- Dry and more moderate (closer to normal) temperatures on Tuesday, with increasing rain chances the rest of next week.

DISCUSSION

Issued at 111 PM EDT Sat Aug 15 2026

Much like the last few days, scattered, short-lived showers and thunderstorms this afternoon and evening will have a low end potential for damaging wind gusts. Cells that track over the same locations could result in some minor flooding issues. Patchy fog will form tonight in areas that receive rain this afternoon, or in valleys.

The mid/upper level ridge over the Deep South today retrogrades and flattens out tomorrow, keeping the track of MCSs in the OH Valley/Great Lakes region to our north. The shift of the ridge appears to bring some drier air aloft, as PWs drop down to 1.3-1.6 inches. Forecast soundings show a stronger cap atop a deeper mixed layer as well, so we should see less convective development in the afternoon compared to the last few days. Some isolated showers/storms are possible in SW VA and the TN mountains. The reduced rain chance and cloud cover should result in ample diurnal heating that will bring temperatures into the 90s for most locations. Although boundary layer mixing will lower afternoon dewpoints a bit (lower to mid 70s), we should still see Heat Index values of 105-110 in the central and southern TN Valley.

On Sunday night, the NAM and some CAMS show remnant MCS convection moving across southern WV, possibly clipping our SW VA counties. The overnight timing will not be favorable for any severe threat.

A greater threat of severe storms may come on Monday. A shortwave trough and a surface cold front will be crossing KY in the morning, likely initiating convection as it moves closer to the Cumberland Plateau in the afternoon. The air mass ahead of the front will remain capped into the early afternoon and have plenty of MLCAPE, around 3000 J/kg, and there will be some shear present in northern sections, around 30-40 kt of 0-6 km shear shown by the NAM. Also concerning is the low level temp/dewpoint profile in model soundings (NAM and GFS), which show an inverted-V profile with steep lapse rates and a deep boundary layer, favorable for damaging wind gusts. DCAPE values in these soundings are 1000-1500 J/kg. The RRFS shows a pretty intense convective line moving through the area between 7 pm and 11 pm. The HRRR does not yet go out into Monday afternoon, but it does develop a convective complex in central and eastern KY in the morning. Wording in the HWO will be beefed up to address this potential severe threat.

The Heat Index on Monday may continue to be in the range for an Advisory in the central and southern TN Valley, but will let the mid shift handle the extention if it is needed. The deep boundary layer mixing that is expected on Monday may drop dewpoints further than currently expected, and could keep the Heat Index just under criteria.

The surface front pushes through the area Monday night. This should bring some slightly lower temperatures and dewpoints for Tuesday, ending the dangerous heat potential but still close to normal temps. The ridge will continue to retrograde the rest of the week, putting a broad trough across the eastern Conus. This will increase our rain chances through the week as embedded shortwaves move through the larger trough and the jet stream drops into the OH Valley.

AVIATION

(18Z TAFS) Issued at 111 PM EDT Sat Aug 15 2026

Scattered showers/storms through the rest of the afternoon have a chance of affecting a TAF site, mainly TYS and TRI based on current radar trends. This activity should end around 22-00Z. Fog appears likely at TRI again tonight, and the chance of LIFR to VLIFR conditions will be higher if a shower crosses the terminal this afternoon.

PRELIMINARY POINT TEMPS/POPS

Chattanooga Airport, TN 76 98 77 98 / 0 0 0 30 Knoxville McGhee Tyson Airport, TN 75 96 76 95 / 10 0 0 50 Oak Ridge, TN 74 94 74 94 / 10 0 0 50 Tri Cities Airport, TN 71 89 71 89 / 0 10 10 70

MRX WATCHES/WARNINGS/ADVISORIES

NC...NONE. TN...Heat Advisory until 8 PM EDT /7 PM CDT/ Sunday for Anderson- Bledsoe-Bradley-Hamilton-Knox-Loudon-Marion-McMinn-Meigs- Morgan-North Sevier-Northwest Blount-Northwest Monroe-Rhea- Roane-Sequatchie-West Polk.

VA...NONE.