textproduct: Huntsville

KEY MESSAGES

Updated at 1014 PM CDT Sun Jul 19 2026

- A Heat Advisory will be in effect for most of the Tennessee Valley for the today through Tuesday at 7 PM.

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

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

NEAR TERM

(Today) Issued at 350 AM CDT Mon Jul 20 2026

A few showers have developed over the past two hours over portions of NW Alabama. Mesoscale guidance is hinting this may continue on and off for a few more hours. Elsewhere, areas of fog have been developing over the last few hours, as highs clouds dissipated. There are some low clouds in place below them, but not enough to keep more areas of fog developing over the next few hours.

Mesoscale guidance seems to want to increase this low level cloud cover (around 850 mb) into the daybreak hours, especially over southern middle Tennessee and areas near west of the I-65 corridor. However, not seeing that occur as much as models were predicting so far. Given light winds already in place and a fair amount of fog development seen in 2.30-10.35 RGB imagery satellite imagery, a Dense Fog Advisory for our southern middle Tennessee and portions of NE Alabama (Madison, Jackson, and DeKalb counties) may be need within the next hour to go through 7 AM. This fog should burn off rather quickly after sunrise. Temperatures will remain warm when you wake up this morning, only dropping into the 70 to 75 degree range. A Heat Advisory remains in effect for today with expected heat index values reaching the 105 to 107 degree range.

Several models show a medium chance of shower and thunderstorm development this afternoon. Given high PWAT values and expected instability, heavy rainfall and frequent lightning could occur with stronger thunderstorms. Localized flash flooding may occur as well.

SHORT TERM

(Monday night through Wednesday) Issued at 1014 PM CDT Sun Jul 19 2026

As has been the case the past few nights, showers that form should fade as we go into Mon night. We cannot rule out patchy later night fog in areas that receive wetting rainfall, as well as fog favored spots. Another muggy and humid night with lows in the low/mid 70s. The milder lows in the mid 70s would help set the stage for more heat issues Tue. Inland deep moisture transport from the Gulf of America should be limited by the tropical entity, thus with lower rain chances, hot conditions will again rule. High temperatures should warm into the low/mid 90s, with heat index values from the upper 90s to 109 degrees. Will have the Heat Advisory continuing into early Tue evening.

Sultry conditions are expected Tue night, as low temperatures cool only into the mid 70, with some upper 70s in the more urbanized heat islands. Depending upon how much of the area will be impacted by clouds and showers in later forecasts, the heat advisory may be needed for some of the area Wed. Very warm upper ridging that was positioned over the central High Plains earlier in the week, should weaken somewhat and build more towards the SW. While this occurs, a system moving in the main westerlies over Canada will induce more troughing from the Great Lakes to the Mid Atlantic in the mid week. This will help bring a surface cold front towards the forecast area on Wed. Lift provided by the front, along with medium to high shower and thunderstorm chances (greater rain chances east) will help provide relief from the heat. Highs should be a tad cooler, from the mid/upper 80s east to low/mid 90s west, with heat index values from the mid 90s to 105 in a few spots. Conditions should cool down a little more Wed night with lows falling into the upper 60s to around 70.

LONG TERM

(Wednesday night through Sunday) Issued at 1014 PM CDT Sun Jul 19 2026

The passage of a cold front on Wednesday will mark the start of the long term forecast with slightly lower temps and dew points. Highs through the long term period will be relegated to the low 90s with dew points dropping back to the high 60s to low 70s. The passage of the cold front will mark a pattern change with a troughing east/ridging west regime setting up through the long term forecast. As such, we will find ourselves solidly in NW flow as we head into the weekend and into early next week. This will keep medium rain chances in the forecast as several shortwaves ripple along the base of the trough. This set up does favor MCSs dropping south along the base of the trough, potentially into our area. As the set up draws nearer, we will continue to evaluate MCS potential and any increased threats for severe weather or flooding.

AVIATION

(12Z TAFS) Issued at 558 AM CDT Mon Jul 20 2026

An area of showers has developed east of the KMSL terminal. Despite that, VFR conditions are currently in place at this terminal, as well as the KHSV terminal. Newer guidance does suggest this activity could spread east to near the KHSV terminal through 15Z before dissipating. However, confidence in coverage is low at the terminals, so only included a PROB30 group for -SHRA for now with MVFR VSBYS at times. Most guidance shows this activity possibly weakening, but then increasing in coverage again early this afternoon. For now, kept close to the current forecast with VCSH in at KMSL after 18Z and at KHSV after 19Z. A tempo group between 18Z and 22Z at KMSL/19Z and 23Z at KHSV was included to address a higher chance of -TSRA activity. MVFR CIGS were included, but may need to be amended if IFR or lower VSBYS/CIGS develop. Expect activity to dissipate after 21/01Z. May have to watch for fog development towards the end of the TAF period, but left it out for now.

HUN WATCHES/WARNINGS/ADVISORIES

AL...Heat Advisory from 10 AM this morning to 8 PM CDT Tuesday for ALZ001>009-016.

TN...Heat Advisory from 10 AM this morning to 8 PM CDT Tuesday for TNZ076-096-097.