textproduct: Huntsville

KEY MESSAGES

Updated at 945 PM CDT Fri Jun 26 2026

- There is a medium (40-60%) chance of thunderstorms tomorrow and tomorrow evening, focused across southern Middle TN and northeast AL. A few storms will be capable of producing locally damaging winds up to 50-60 MPH. Otherwise, lightning and heavy rainfall will be the main storm impacts.

- The first big heat wave of the summer moves in Sunday and continues through all of next week. HeatRisk values of Major and Extreme (Levels 3 and 4 out of 4) indicate impactful heat all week, coupled with Heat Index values of 100-109 F.

NEAR TERM

(This Evening through Saturday) Issued at 945 PM CDT Fri Jun 26 2026

In the mid/upper-levels, a zonally-oriented ridge will extend from subtropical parts of the eastern North Pacific across the northern Gulf and into the central North Atlantic for the duration of the near term period. Embedded within prevailing WNW flow aloft of 20-30 knots (along the northern rim of the ridge) a series of weak vorticity maxima (perhaps convectively-enhanced) will shift eastward from the southern High Plains through the OH/TN Valleys and off the Mid-Atlantic Coast. One initially prominent disturbance will lose definition as it tracks eastward to the north of the forecast area overnight. However, it will remain sufficiently organized to sustain a west-southwesterly low- level jet of 15-25 knots, with the related increase in low-level warm advection supporting a thick layer of altostratus clouds that will remain intact through at least early tomorrow afternoon.

Isolated light showers within this regime may bring a few sprinkles of rain to northwest AL/southern Middle TN early this evening, but this weak convection is likely to dissipate between 3-6Z. Well to our northwest, an outflow boundary originating from storms earlier today across southern MO is expected to spread southeastward with time and may ignite new thunderstorms across western portions of KY/TN during the predawn hours. Although the southward extent of this regime in the 9-12Z timeframe is unclear at this point, the majority of impacts across our region are likely to come after 12Z and we will only leave a 10-20% POP in place across northwest AL/southern Middle TN. Should any nocturnal convection impact our region, it is not expected to be strong- severe, but will certainly be capable of producing lightning and locally heavy rainfall. Otherwise, the combination of increasingly overcast skies and a light SW wind will yield a warm night with lows in the l-m 70s.

During the late morning hours tomorrow, convective outflow from a growing cluster of rain and thunderstorms to our north will begin to spread very slowly southward across the AL-TN border, perhaps initiating development of new convection across southern Middle TN. However, within a synoptic environment characterized by gradual 500-mb height rises (and only weak low-level ascent along and immediately north of a surface cold pool)we anticipate a sharp gradient in precipitation coverage, with locations south of the TN River expected to experience very little (if any) rain, while locations in southern Middle TN and northeast AL currently have POPs in the 40-60% range. Regeneration of thunderstorms is expected to occur across eastern AR/western TN by mid-day as another prominent mid-level wave begins to track eastward and interact with the outflow boundary from morning storms, and this could result in additional storms that would impact the same portion of our CWFA late tomorrow afternoon and evening. The local storm environment will feature CAPE around 2000 J/kg and steep low-level lapse rates as temps warm into the u80s-l90s. This, along with deep-layer shear marginally conducive for storm organization, will support locally damaging winds (up to 50-60 MPH), frequent lightning and heavy rain as the main storm impacts. Although low-level flow appears too weak to support a risk for brief tornadoes, shear in the 0-3km layer may lead to occasional mesocyclone development with the stronger updrafts.

SHORT TERM

(Saturday night through Monday night) Issued at 945 PM CDT Fri Jun 26 2026

Showers and thunderstorms will likely be ongoing across portions of southern Middle TN and northeast AL early Saturday evening, and this regime could persist into the early morning hours on Sunday. However, the axis of convection will gradually spread northeastward and out of the region by sunrise, as a mid-level high centered across the Lower MS Valley amplifies northward into the Upper MS Valley downstream from a longwave trough across the western CONUS. As the anticyclone aloft begins to strengthen and expand northeastward into our region on Sunday, mid/upper-level winds will diminish and veer to the north, with an increasing influence from broad scale subsidence expected to keep diurnal convection concentrated to our immediate east on both Sunday and Monday afternoons. Nevertheless, we will maintain a very low (10-20%) POP for our far eastern forecast zones to account for some uncertainty regarding the precise location of the 500-mb high.

By the end of the short term period (Monday night), the center of the subtropical ridge is predicted to migrate northeastward into western KY, placing the local forecast area beneath strengthening ENE flow aloft. This may allow a few thunderstorms (driven by both outflow and a weak vort max traveling around the southeastern flank of the ridge) to spread westward into the forecast area during the evening hours. Should this occur, high values of both CAPE and DCAPE will support a risk for strong downburst winds with this activity. Otherwise, the primary weather impact during the short term period will be excessive heat, with afternoon highs rising into the l-m 90s Sunday and mid to (perhaps) upper 90s on Monday. Although mixing of low-level moisture on a daily basis may occasionally result in dewpoints falling into the mid 60s, this will not occur everywhere and heat index will likely reach the 100-105F range for most of the valley on Sunday/Monday (with 105-110F possible in portions of the forecast area on Monday).

LONG TERM

(Tuesday through Friday) Issued at 945 PM CDT Fri Jun 26 2026

The long term forecast will be influenced by a persistent 594dam high aloft, leading to the first real heat wave we have seen this year. This high will be anchored over the OH Valley down through the TN Valley through much of the work week and will likely keep heat related advisories in place over multiple days. The heat threat will come from the combination of temps in the 90s (upper 90s some afternoons) and dewpoints in the low to mid 70s that will bring heat indices to the 100-105 degree range. In addition, overnight lows in the mid to upper 70s will provide very little relief from the warm and humid conditions during the day, keeping us in a Major HeatRisk through the long term period. While the forecast looks relatively dry during this period, low (10-30%) chances for diurnal thunderstorms will exist each afternoon and could keep some locations from reaching the higher heat indices mentioned above. Please keep up with the latest forecast as we head into next week. Those with outdoor plans should prioritize heat safety by staying hydrated, wearing light colored clothing, taking frequent breaks in the shade or A/C, using sunscreen, and never leaving people or pets behind in vehicles.

AVIATION

(06Z TAFS) Issued at 1208 AM CDT Sat Jun 27 2026

VFR conditions are forecast through tonight into Saturday morning. By the late morning hours into the afternoon, a low chance of MVFR conditions have been continued as a PROB30 group due to decreased visibilities and ceilings as showers/thunderstorms begin to impact the area. VFR conditions are forecast to return during the early evening and persist through the end of the TAF period.

CLIMATE

Issued at 605 PM CDT Thu Jun 25 2026

Moderate to High Risk for Much Above Normal Temperatures:

The Climate Prediction Center has included the Tennessee Valley in a High Risk for Much Above Normal Temperatures for July 3. Therefore, there is a 60-80% chance for temperatures above above the mid 90s and Heat Index values above 105 degrees F during this period.

The Climate Prediction Center has included the Tennessee Valley in a Moderate Risk for Much Above Normal Temperatures for July 4. Therefore, there is a 40-60% chance for temperatures above above the mid 90s and Heat Index values above 105 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...None. TN...None.