textproduct: Huntsville

KEY MESSAGES

Updated at 1020 PM CDT Wed Sep 16 2026

- A Heat Advisory is in effect through 8 PM Saturday across all of southern middle Tennessee and northern Alabama.

- NWS Heat Risk highlights Moderate (Level 2/4) to Major (Level 3/4) heat impacts through the weekend across the Tennessee Valley. Localized Extreme (Level 4/4) impacts may occur in urbanized areas.

NEAR TERM

(This Evening through Thursday) Issued at 1020 PM CDT Wed Sep 16 2026

A strong mid-level high (initially positioned across East TN) will continue to migrate west-southwestward over the course of the near term period, becoming centered across southwestern AR by 0Z Friday. As this occurs, N-NE flow will become established across the TN Valley tonight and should increase into the 10-20 knot range tomorrow as a developing upper low retrogrades across the southwestern North Atlantic and approaches the FL Peninsula late in the period. In the low-levels, our forecast area will continue to be influenced by a weakening surface high as it shifts eastward into the northwestern Atlantic, with a light SSE-calm wind anticipated overnight, followed by light/variable flow (within a relaxing pressure gradient) tomorrow. Due to a more favorable environment for radiational cooling, development of patchy, early- morning mist and fog appears a bit more likely tonight as temperatures drop into the u60s-l70s.

In similar fashion to the past several days, temperatures will begin to increase quickly after sunrise, and with continuing influence from the departing mid-level ridge, only a scattered cumulus field is expected. Thus, highs will once again range from the u80s-l90s in elevated terrain to the m-u 90s in the valley, with dewpoints mixing down into the m60s keeping heat indices in the 98-102F range for most of the region. However, with Heat Risk largely in the Level 2/3 range and high temps running 5-10F above normal (low temps running 10-15F above normal), we will retain the preexisting Heat Advisory to highlight impacts from this recent stretch of hot weather. Although a few, small and low-topped showers may evolve during the crest of the diurnal warming cycle tomorrow afternoon, the coverage of showers and thunderstorms should be higher to our north/east as an MCV traveling around the northeastern periphery of the ridge aloft enhances lift across the central/southern Appalachians. Thus, rain chances for our region will remain in the 5-10% range (slightly higher in the elevated terrain of northeast AL/southern Middle TN).

SHORT TERM

(Thursday night through Saturday night) Issued at 1020 PM CDT Wed Sep 16 2026

Throughout the short term period, a weakening subtropical high in the mid-levels will remain centered over the Arklatex as a developing upper low travels west-southwestward across the FL Peninsula and into the eastern Gulf. This configuration will sustain N-NE flow aloft of 10-20 knots, although gradual moistening of the lower tropospheric column will support a minor increase in PWAT as we progress through the period (with values rising back to 1.6-1.7" early this weekend).

Latest guidance still suggests that a Canadian surface high will translate southeastward across OT and into southern QC from Thursday night-Friday night, with a cold front edging slowly southwestward between the Lower Great Lakes and OH Valley. It still appears as if a prefrontal wind shift axis will initiate afternoon convection from the OH Valley into the southern Mid- Atlantic states on Friday, with a greater coverage of terrain- induced thunderstorms across the southern Appalachians, as well. Storm coverage will likely be a bit higher across our CWFA (particularly the eastern half) during the afternoon and evening hours due to the diminishing influence of the subtropical ridge. However, this will be contingent on a source of low-level ascent (likely a combination of convective outflow and topography). Should stronger updrafts manage to develop in our region, the thermodynamic environment Friday afternoon will support locally damaging downburst winds, along with frequent lightning.

As the weakening Canadian surface high shifts eastward across New England on Saturday/Saturday night, minor pressure rises in the lee of the southern Appalachians will induce light SSE flow across our region, with scattered diurnal convection and a similar risk for locally damaging downburst winds on Saturday (and continuing into Saturday evening) expected to be focused along the interface of this regime. Afternoon highs and overnight lows will exhibit little fluctuation through the short term period, and in order to highlight Heat Risk values in the Level 2/3 range, we will maintain a Heat Advisory through 8 PM Saturday.

LONG TERM

(Sunday through Wednesday) Issued at 1020 PM CDT Wed Sep 16 2026

Extended range model data suggests that light S-SW flow in the low-levels will exist across the region from Sunday into Monday, as a weak area of low pressure tracks east-northeastward from the Ozarks into northern parts of the TN Valley. This will sustain a warm and increasingly moist airmass, with highs remaining in the m-u 90s (in lower elevations) and an isolated-widely scattered coverage of mainly afternoon/early evening showers and thunderstorms. During the timeframe from Monday night into Tuesday, the weakening area of low pressure to our north will evolve into a frontal wave as it lifts further northeastward into the Upper OH Valley, with a general increase in the spatial coverage of showers and thunderstorms anticipated both periods as the trailing cold front drifts southeastward. Whether or not the front continues to advance southeastward (and brings our forecast area a slightly cooler/drier airmass on Tuesday night/Wednesday) remains up for debate, and will likely be dependent on amplification of an upper-level trough to our north. Regardless, we will advertise slightly cooler high temps (u80s-l90s) by Wednesday.

AVIATION

(06Z TAFS) Issued at 1141 PM CDT Wed Sep 16 2026

VFR conditions will prevail through the period, with light winds and a mostly clear sky. The one exception may be briefly early Thursday morning when some light MVFR fog may develop. Have included a TEMPO between 10-13z to account for this. Any fog that does develop will dissipate by mid morning.

HUN WATCHES/WARNINGS/ADVISORIES

AL...Heat Advisory until 8 PM CDT Saturday for ALZ001>010-016.

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