textproduct: Huntsville

KEY MESSAGES

Updated at 130 PM CDT Sat Jul 18 2026

- Moderate (Level 2/4) to Major (Level 3/4) Heat Risk will build into the Tennessee Valley this weekend through the middle of next week, with peak heat index values between 100 to 105 degrees likely, and potentially between 105-109 degrees in some locations Monday and Tuesday.

- Daily thunderstorm chances will continue over the weekend into early next week. A few storms could become strong to marginally severe, especially on Sunday. Gusty to damaging winds and locally heavy rainfall will be the main threats.

- Slightly cooler and less humid air is expected in the middle and latter portions of next week.

NEAR TERM

(Tonight) Issued at 130 PM CDT Sat Jul 18 2026

A few remnant outflow boundaries have served as a focus for some clusters of thunderstorms along the AL/GA border and across portions of northwest Alabama early this afternoon. There is plenty of instability to work with MLCAPE values around 2000-3000 J/kg coupled with low-level lapse rates around 7.5 C/km. DCAPE values are a little more modest, but still appreciable (around 600-700 J/kg). These values will support at least a few localized strong storms through the early evening hours. Radar coverage at 18z was a touch higher than forecast, so have adjusted PoPs up to 30-50% for the remainder of the afternoon. Otherwise, heat will remain the biggest concern through the remainder of the day with peak heat index values between 100-105 degrees.

This activity will wane after sunset, with tranquil conditions again forecast overnight (save for some patchy fog in areas that receive rainfall).

SHORT TERM

(Sunday through Tuesday) Issued at 912 AM CDT Sat Jul 18 2026

A Moderate (Level 2/4) to Major (level 3/4) Heat Risk will be the main concern in the forecast early next week with high pressure building in and a tropical-like air mass in place under the ridge. This will create daytime highs in the low to mid 90s each day, with heat index values between 100-105 degrees across the entire Tennessee Valley (and several locations that reach the 105-109 degree range by Monday and especially Tuesday). Heat products may be needed by early next week and we will continue to monitor forecast trends. Regardless, it will be important to practice heat safety next week, especially if you have outdoor plans!

Daily thunderstorm chances will exist each afternoon, thanks to diurnal heating and residual outflow boundaries in place. The greatest coverage will likely occur on Sunday as a weak shortwave clips the northeast edge of the ridge, with medium (40-60%) chances for showers/storms. MLCAPE values of 2500-3000 J/kg, DCAPE values over 1000 J/kg, and low-level lapse rates of 8-9 C/km will favor at least a few strong to marginally severe storms capable of producing damaging winds and heavy rainfall. SPC has placed the entire Tennessee Valley under a Marginal Risk (Level 1/5) for severe weather for this reason.

As the ridge builds east, PoPs will lower to 30-50% on Monday and 20-40% on Tuesday thanks to stronger subsidence and a lack of forcing. Each day there will be a low chance of a couple storms becoming locally strong to marginally severe, with gusty/damaging winds and heavy downpours the main threat.

LONG TERM

(Monday night through Friday) Issued at 858 PM CDT Fri Jul 17 2026

The weather pattern during the day 4-7 period will involve a strong trough developing over the Great Lakes into the mid Atlantic and New England states and an upper ridge building over the southern Plains. A low level thermal ridge (850 mb temps of 20-23C) will arrive on Tuesday, making for a hot and humid day. Heat Risk will reach the Major category (3 out of 4) for much of the TN valley. High temperatures in the lower to middle 90s, heat index values of 100 to ~105F and WBGTs in the middle to upper 80s are expected. A shortwave trough axis and cool front will drop southeast toward the TN Valley through the TN Valley on Wednesday, bringing a low chance of thunderstorms. Behind the front, slightly cooler air with highs in the upper 80s to lower 90s are expected Wednesday, with middle to upper 80s on Thursday after morning lows in the middle to upper 60s. Another Friday morning lows in the 60s, afternoon highs will be near normal and in the upper 80s to around 90. And even better, dew points will drop into the middle to upper 60s Friday.

AVIATION

(00Z TAFS) Issued at 542 PM CDT Sat Jul 18 2026

Any lingering thunderstorms should wane at the start of the period leaving VFR conditions in place through around 20Z tomorrow. Around and after 20Z, scattered showers and thunderstorms will develop and remain through the end of the TAF period. Should a storm move directly over the terminal this could lower ceilings and visibilities, however confidence in storm location and exact timing is too low at this time to include a tempo group.

HUN WATCHES/WARNINGS/ADVISORIES

AL...None. TN...None.