textproduct: Huntsville

KEY MESSAGES

Updated at 355 AM CDT Sun Aug 16 2026

- Dangerous heat will impact the Tennessee Valley today, with Major (Level 3/4) to Extreme (Level 4/4) heat impacts forecast. Some relief is expected Tuesday, but the heat returns Wednesday and Thursday.

- A Heat Advisory is in effect for all of northern Alabama and southern middle Tennessee through 7 PM this evening, with extensions on the table in future updates into the mid- week. - A Slight (2 out of 5) risk for severe thunderstorms is forecast today across eastern Franklin County Tennessee and portions of far northeast Alabama, with a Marginal (1 out of 5) risk for most of the area.

NEAR TERM

(Today) Issued at 355 AM CDT Mon Aug 17 2026

As has been the case the last few days, strong upper ridging across the southern CONUS has been the main feature controlling our sensible weather. This ridging however was showing signs of slight weakening, with it shifting more to the south and west of the region. Also, an upper low over central Canada should move to the SE across northern Ontario to the southern Hudson Bay in the mid week. This will induce synoptic scale troughing across the eastern CONUS from the midweek onward, and bring more seasonable conditions to the region.

Before then, we have at least one more day of very warm to hot conditions. High temperatures later today once again should soar into mid/upper 90s, with corresponding heat indexes from the upper 90s to 110 degrees. We do have some higher heat indexes (HI), but coverage of them is too low to warrant going to an Extreme Heat Warning at this time. Another factor of more mixing that could lower dewpoints and the HI. A third item, more clouds accompanying a cold front approaching from the NW.

This front was positioned from the southern Great Lakes to the OK/TX Red River Valley. This boundary should head to the SE during the course of the day, reaching the Tennessee Valley this afternoon into the evening. Scattered to numerous showers and thunderstorms were already in progress from parts of SE Missouri to southern Ohio, preceding the front. Strong daytime heating ahead of this front of a very moist environment will produce surface based CAPES over 2000 J/kg, with a noticeable inverted-V forecast in soundings this afternoon. That and a linear 20-30 kt environmental shear will allow strong to severe thunderstorm development. The main threat will be damaging downburst-type wind gusts over 60 mph. Precipitable water amounts from 1.8" to 2.1" supports torrential downpours in the heavier showers and/or stronger storms.

SHORT TERM

(Tonight through Wednesday) Issued at 956 PM CDT Sun Aug 16 2026

Convection will wane in the evening hours as the boundary drops south of the region. Some patchy fog may develop in locations that receive rainfall late Monday, but otherwise it should be a fairly tranquil night. An ever so subtle change to the air mass may take place Tuesday as dewpoints will run a little lower and subsequently heat index values in the 100-105 degree range will be more common. Still, Moderate (Level 2/3) to Major (Level 3/4) heat impacts are forecast and everyone should still observe common sense heat safety. Heat impacts will temporarily creep back into the region on Wednesday as highs return to the mid to upper 90s and dewpoints in the 70s push peak heat index values above 105 degrees over much of the area.

LONG TERM

(Wednesday night through Sunday) Issued at 956 PM CDT Sun Aug 16 2026

After Wednesday, the upper-ridge will begin to flatten and shift back to the west over the southern Rockies and Great Basin. This will place the Tennessee Valley into northwest flow aloft, opening us up to a couple of shortwaves that will push through the area Thursday and Friday, resulting in medium (30-60%) chances for showers and thunderstorms both afternoons. A front will sag south of the area by the weekend, keeping the better chances for showers and storms displaced to south of us across central and south Alabama. This will also give us a relative break from the heat as highs will drop to the upper 80s to lower 90s, with overnight lows in the 60s by the weekend.

AVIATION

(06Z TAFS) Issued at 1254 AM CDT Mon Aug 17 2026

For the most part, VFR flight conditions should continue for the greater TN Valley. But a few reports of patchy fog have been noted around the region thanks to moisture loaded environment. We cannot rule out an instance of fog impacting a terminal before daybreak, with chances of it too low to mention in the TAF. More notable is a cold front moving to the region this afternoon and evening. With strong daytime heating and high instability, convection should form this afternoon. Some of the storms could produce strong to severe outflow wind gusts, as well as heavy downpours from lowered CIG/VSBY. Shower activity should fade after sunset with VFR conditions expected thereafter.

HUN WATCHES/WARNINGS/ADVISORIES

AL...Heat Advisory until 7 PM CDT this evening for ALZ001>010-016.

TN...Heat Advisory until 7 PM CDT this evening for TNZ076-096-097.