textproduct: Huntsville

KEY MESSAGES

Updated at 157 PM CDT Wed Aug 12 2026

- A Heat Advisory is in effect for the entire forecast area Today through Sunday, with extensions likely into the middle of next week.

- A low conditional threat for strong to severe storms will exist once again this afternoon.

NEAR TERM

(Tonight) Issued at 157 PM CDT Wed Aug 12 2026

Diurnal heating has triggered several showers and thunderstorms across the Tennessee Valley a little earlier than anticipated today. This activity is solely tied to diurnal heating and with favorable thermodynamics allowing any of these storms to become strong to marginally severe through this evening. DCAPE values around 1000-1200 J/kg would favor damaging downbursts as the primary threat. Additionally, PWATs over 2" and slow storm motions will also result in a locally heavy rainfall and flash flooding concern (with locations that do receive repeated rainfall). Given the slightly higher coverage, have increased PoPs to 30-50% through early this evening.

Additionally, we'll again need to watch convection upstream over the Ohio Valley in Illinois and Indiana. If it holds together, the steering flow could push a few clusters of elevated, subsevere storms through the area overnight. A few Hi-Res solutions now show some of this convection clipping the area which makes sense given the current location of storms to the northwest and the position of synoptic features. Thus, will leave a low chance for showers and elevated storms overnight, especially in the eastern half of our area.

Finally, heat will continue to be concern not only during the afternoon, but also overnight as there will be very limited relief (with lows in the mid to upper 70s). The Heat Advisory remains in effect for the entire Tennessee Valley region.

SHORT TERM

(Thursday through Friday night) Issued at 832 AM CDT Wed Aug 12 2026

A large area of high pressure will build into the Tennessee Valley from the west late this week, with a heat dome underneath this ridge subsequently shifting east into the region. Ample sunshine will warm temperatures will the mid to upper 90s and combine with dewpoints in the mid to upper 70s will create dangerous heat indices in the 105-110 degree range. NWS Heat Risk highlights a Major Risk (Level 3/4) of heat related impacts during the day (and overnight as lows will remain in the mid to upper 70s). Thus, a Heat Advisory is in effect for this entire period and now runs through 7 PM Sunday. Another low chance (20-30%) of showers and storms is forecast again Thursday afternoon, but by Friday strong subsidence from the ridge should prevent any pulse convection from forming and PoPs will drop to below 10%.

LONG TERM

(Saturday through Tuesday) Issued at 1045 PM CDT Tue Aug 11 2026

Extended range data from the latest suite of global models is in general agreement that a subtropical high (centered from the Lower MS Valley to the southeastern Atlantic Coast) will continue to strengthen this weekend, with geopotential heights perhaps reaching 600 dam. Thus, excessive heat will continue to be a concern across the TN Valley, with highs remaining in the m-u 90s from Saturday-Monday (and perhaps exceeding 100F in several locations on both Sunday and Monday afternoons). Although a few afternoon storms may occur on both Saturday and Sunday (primarily in the higher terrain of northeast AL), rain chances will remain low and there is a very high chance that the pre-existing Heat Advisory will need to be extended through Monday, perhaps with an upgrade to an Extreme Heat Warning due to Heat Index readings surpassing 110F. By late in the forecast period, there are indications that the subtropical high may begin to retrograde into the southern High Plains, perhaps allowing NW flow aloft to become reestablished across our region by Monday/Tuesday. Should this occur, a weak cold front may bring a broken line of showers and thunderstorms to the region Monday evening, followed by a slight drop in temperatures/dewpoints on Tuesday.

AVIATION

(00Z TAFS) Issued at 726 PM CDT Wed Aug 12 2026

Regional radar data indicates a few remaining clusters of TSRA traveling east-southeastward across northern AL early this evening. With this activity predicted to dissipate by 2Z, we will not include it in the 0Z TAFs, but will monitor trends in the event that a short-fused amendment or AWW (for lightning) is warranted. During the early morning hours tomorrow, there is some concern that outflow-generated convection (from storm clusters currently in progress across the OH Valley) may once again enter portions of the forecast area (particularly northeast AL). Due to a considerable amount of uncertainty regarding the timing and coverage of this activity we will also refrain from mentioning in the current forecast. Presuming no convective impacts, patchy BR/FG may reduce vsby to MVFR-levels at both airports btwn 9-13Z (as both terminals reported measurable rainfall earlier today). SW flow will increase to 5-10 kts once again by 15Z, with development of a scattered Cu field expected around this time, as well. Although a few storms may occur in the general region late tomorrow aftn, the threat for impacts at the terminals is too low to mention in the forecast attm.

CLIMATE

Issued at 157 PM CDT Wed Aug 12 2026

The Climate Prediction Center has included much of northern Alabama in a High Risk for Much Above Normal Temperatures and much of southern middle Tennessee and far northeast Alabama in a Moderate Risk for Much Above Normal Temperatures on August 20th and 21st.

All of northern Alabama and southern middle Tennessee is also included in a Moderate Risk for Much Above Normal Temperatures August 22nd and 23rd.

Therefore, there is a 40-60% chance in the Moderate Risk locations and a 60-80% chance for those in the High Risk areas for temperatures above 95 to 97 degrees F and heat index values above 105 to 110 degrees F during this period.

More information on the CPC U.S. Hazards Outlook can be found at:

https://www.cpc.ncep.noaa.gov/products/predictions/threats/threats.php

HUN WATCHES/WARNINGS/ADVISORIES

AL...Heat Advisory until 7 PM CDT Sunday for ALZ001>010-016.

TN...Heat Advisory until 7 PM CDT Sunday for TNZ076-096-097.