textproduct: Huntsville

KEY MESSAGES

Updated at 402 AM CDT Tue Jul 21 2026

- A Heat Advisory is in effect for most of the Tennessee Valley through 8 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 most locations today and Tuesday.

- Daily thunderstorm chances will continue before ending later in the day on Wednesday. A few storms could become strong to marginally severe this evening into early Wednesday morning. Gusty to damaging winds, frequent lightning, and locally heavy rainfall will be the main threats.

NEAR TERM

(Today) Issued at 402 AM CDT Tue Jul 21 2026

Clear skies continue to be in place across northern Alabama and southern middle Tennessee. Expect that to continue through daybreak. Given current dew point depressions, patchy fog will continue to be possible through the daybreak hours. Advection of lower dewpoints from the NE should help to keep dense fog from forming though given upstream weak flow seen at 1000 mb from the east or southeast.

Expect more scattered clouds to form over the area after daybreak. These clouds should not have much impact on area temperatures. Expecting a warmer day today than yesterday as a result with high temperatures climbing into the 92 to 95 degree range in many locations. With a front pushing south towards the area this evening, higher dewpoints should be focused over our area again today in the mid to late afternoon hours into the evening hours. This will drive heat index values into the 105 to 109 degree range in many locations as well. The exception to this looks to be DeKalb county and portions of Jackson county. Models continue to keep the area dry through the afternoon hours. A Heat advisory remains in effect through 8 PM this evening.

SHORT TERM

(Tuesday night through Thursday) Issued at 610 AM CDT Tue Jul 21 2026

At sunset, storms will likely be on the horizon to our north along an approaching cold front. Models maintain a later arrival of storms, between 9 PM - 12 AM. Fortunately, the later arrival will allow time for instability to erode, leaving only a few hundred J/KG of CAPE by the time storms get here. Models diverge on coverage of showers and storms. Some dissipate storms as they arrive and others drag a broken line of storms through, dissipating as they go. What is consistent is the lack of shear, meaning regardless of the actual coverage of storms, any storms that do make it through will obtain only a low severe threat with the primary hazard being damaging winds.

The actual front looks to push through most of the area Wednesday morning. However, some models do show the front lingering over or just southeast of Cullman/Marshall/DeKalb counties into Wednesday afternoon. At this point, storms do not look severe. Then most guidance pushes it further southeast of the area, but stalls the boundary just to the southeast of Cullman/Marshall/DeKalb counties. High temperatures on Wednesday will be relegated back to the upper 80s/low 90s due to cloud cover and lingering scattered precipitation chances. Dewpoints will drop through the day on Wednesday into the 65 to 70 degree range primarily.

The stalling of the front just to our southeast will keep low to medium shower and thunderstorm chances (30-50%) in the forecast through Thursday for portions of northeastern Alabama into Cullman county. Drier and even cooler temperatures (low/mid 80S) are expected further behind the front in southern middle Tennessee into northwestern Alabama with mid/upper 80s expected south of the Tennessee River.

LONG TERM

(Thursday night through Monday) Issued at 905 PM CDT Mon Jul 20 2026

The general upper level setup will consist of a ridging west and troughing east pattern over the greater North American domain. This pattern was being kept in place by Omega-style upper blocking over the northern Pacific basin. At the beginning of the extended, upper troughing will be in place off of the west coast (the eastern anchor of the upper block), with strong upper level ridging situated over the southern Great Plains. A passing upper low over the central Ontario and Quebec region will deepen, and help amplify upper troughing from the eastern Great Lakes to northern Florida. This will place the Tennessee Valley in a WNW-ESE flow from the late week into early next week.

A northwesterly upper level flow across this area, especially if it is disturbance laden, is known for bringing showers and thunderstorms to the Valley. Convection in these regimes can be accompanied by strong winds. For this area, a few complications to that simplistic view. First, a cold front should be south of the area by late Thu. Moisture from Tropical Storm Bertha should be streaming back to the NE, with some of it impacting the area Fri into Sat. Along with lower level tropical moisture, some of the extended guidance was suggesting that upper level support moving across the area from late Fri into Sun could bring more thunderstorms to the area. It is way too early to discern if this convection could become more significant, given much model uncertainty this far out. With a main synoptic front to our south and with some shower/storm chances, daily high/low temperatures should trend a bit milder, with highs Fri/Sat in the mid 80s to around 90. Warmer conditions look return for the start of the new week, with highs from the upper 80s to lower 90s Sun, and low/mid 90s next Mon. Lows Thu night should range in the mid/upper 60s, with mainly lower 70s for the Fri - Sun night period.

AVIATION

(12Z TAFS) Issued at 610 AM CDT Tue Jul 21 2026

VFR conditions are expeccted at both terminals through much of the TAF period. Southerly winds will increase to between 5 and 10 knots this morning before turning more to the southeast this evening. Confidence is low that any -TSRA will impact either the KHSV or KMSL terminal through at least 3Z (maybe as late as 6Z). However, a PROB30 group for -TSRA was included between 5Z and 11Z for both terminals that lowers VSBYS and CIGS at times to MVFR criteria. This may need to be shifted as we get closer to that timeframe or be made more predominant. For now, confidence is just too low to do anything more than a PROB30 group.

HUN WATCHES/WARNINGS/ADVISORIES

AL...Heat Advisory until 8 PM CDT this evening for ALZ001>009-016.

TN...Heat Advisory until 8 PM CDT this evening for TNZ076-096-097.