textproduct: Huntsville

KEY MESSAGES

Updated at 932 AM CDT Tue Jul 21 2026

- A Heat Advisory is in effect for most of the Tennessee Valley through 8 PM.

- Major (Level 3/4) Heat Risk will develop across the Tennessee Valley today, with peak heat index values between 105 to 110 degrees likely in many locations. - Low chance for a few strong to severe storms tonight into early Wednesday morning along and ahead of a cold front. Gusty to damaging winds, frequent lightning, and locally heavy rainfall will be the main threats.

NEAR TERM

(Tonight) Issued at 147 PM CDT Tue Jul 21 2026

Major Heat impacts continue this afternoon as temperatures in the low to perhaps mid 90s combine with dewpoints in the mid to upper 70s to create heat index values as high as 105-110 degrees. A Heat Advisory remains in effect through 8 PM. Current satellite shows a very flat scattered Cu field in place, with subsidence from the ridge building in from the west evident on model soundings. Despite this, we do have a low to medium chance of showers and storms late this evening and overnight (with a conditional risk that a few could be strong or marginally severe).

A cold front along the Ohio River will serve as a focus for thunderstorms late this afternoon into the evening hours. Upstream from us the environment remains very favorable for severe thunderstorms, but as they push further to the south during the evening hours, the environment becomes less favorable across middle Tennessee and especially into northern Alabama. The latest hi-res guidance continues to maintain a late arrival of this activity into the Tennessee 10 PM to 5 AM (with many solutions favoring after Midnight. Should the storms arrive a little earlier there may be just enough instability to support a low threat for a few strong to severe outflow driven storms. Should this activity move in after 06z, we may struggle to realize thunderstorms, let alone severe weather as any surface-based instability will be very limited as will low/mid-level lapse rates. We'll have to watch trends closely over the next 12-18 hours and adjust PoPs/timing accordingly.

SHORT TERM

(Wednesday through Thursday) Issued at 932 AM CDT Tue Jul 21 2026

On Wednesday, the aforementioned cold front will be pushing through the region during the morning into the early afternoon hours. The storm environment should be fairly worked over thanks the activity overnight into the early morning hours as surface- based instability will be far more limited. However, a low- medium (30-60%) chance for showers and a few storms will exist through the afternoon (especially for locations south of the Tennessee Valley where instability will be slightly higher). The aforementioned rain chances and denser cloud cover will lower temperatures and subsequently heat index values slightly. Still, highs in the upper 80s to lower 90s, and heat index values around the 100 degree mark could create some Moderate (Level 2/4) heat risk concerns.

A slightly cooler and drier air mass will filter into the area in wake of the front on Thursday, with high temperatures dropping into the mid to upper 80s and any appreciable precipitation chances remaining just to the south of the area along the front. As a result, most of the region will be devoid of any diurnally driven convection, save for a low chance (20-30%) clipping our far southeastern zones.

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

(18Z TAFS) Issued at 1133 AM CDT Tue Jul 21 2026

VFR conditions will be the predominant flight category at each terminal through the period. The one exception may be overnight 04-10z when a low chance of showers/storms could cause localized MVFR conditions. Have handled this with a PROB30 for now due to low confidence in this occurring.

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.