textproduct: Huntsville

KEY MESSAGES

Updated at 904 AM CDT Tue May 26 2026

- A Flood Watch for Flash Flooding is in effect through 10 PM Tuesday for Cullman, Morgan, Madison, Jackson, Marshall and Dekalb counties.

- Medium to high chances for showers and thunderstorms continue across the Tennessee Valley into the weekend.

NEAR TERM

(Tonight) Issued at 137 PM CDT Tue May 26 2026

A broad area of low pressure across the Mid South and lower Mississippi Valley and diurnal heating has generated several clusters of showers and thunderstorms across central and southern Alabama, which will continue to push northward into the Tennessee Valley over the next 2-3 hours. Satellite imagery indicates some breaks in the cloud cover, which has allowed most locations to warm into the upper 70s to lower 80s as of 18z. Winds at the surface have now largely veered to the SSW, with SW flow in the mid to upper-levels, straightening hodographs per the latest VWPs at HTX, GWX, and BMX. Still, with effective shear around 20-30 kts and MLCAPE values around 500-1000 J/kg, this may allow for some modestly organized thunderstorms, especially during the late afternoon and early evening window (20-02z).

As noted in this morning's discussion, the primary risk, by far, continues to be locally heavy rainfall and a low chance for flash flooding. Forecasted PWATS between 1.6"-1.7" are between the 95th-99th percentile per BMX/OHX sounding climatology. In particular, locations in the Flood Watch (areas in Alabama along and east of I-65) will be most favored for localized flooding in slower moving convection where training occurs. Thus, we will keep the Flood Watch in effect until 10 PM when these showers and storms will generally wane overnight. Given the recent trends in convection dissipating by the evening and guidance keeping convection more diurnally driven later in the week, think this Flood Watch can most likely be allowed to expire by 03z. With dense cloud cover in place, it will again be a very warm/humid night, with lows in the upper 60s.

SHORT TERM

(Wednesday through Thursday) Issued at 904 AM CDT Tue May 26 2026

A pretty similar pattern will persist Wednesday and Thursday across the Tennessee Valley, though wind shear values will be a bit lower both days. Convection will again be diurnally driven and favored to develop along any lingering mesoscale boundaries from the previous day's convection. Heating should be sufficient enough (with the southwesterly surface flow and enough breaks in the clouds) to push temperatures into the low to mid 80s each afternoon. MLCAPE values around 1000 J/kg will support a few locally strong pulse thunderstorms during peak heating in the afternoon and evening hours. However, the primary threat by far again will be locally heavy rainfall and a low chance of flash flooding given the very moist, tropical air mass in place.

LONG TERM

(Thursday night through Monday) Issued at 1120 PM CDT Mon May 25 2026

Most guidance shows the surface front pushing south of the area by Thursday evening. Cloud cover should linger though behind the front over the area. Not much appreciable cold air advection or drier air shown right behind the front. This combination should keep overnight lows on the warm side in the lower to mid 60s. This should also provide a brief break from rainfall activity.

Most guidance moves the front northward around daybreak on Friday into northwestern Alabama and possibly some of our southeastern counties in AL. Forcing is not very strong, but does move back over the area. Instability between 1000 and 1600 J/KG (some guidance a bit more) does develop by the afternoon hours. Shear though is very weak (~10 to 15 knots). PWATS remain high between 1.6 to 1.8 inches. So a very saturated atmospheric column will not take much forcing to produce heavy rainfall rates. A continue threat for a period of rain and thunderstorms developing during the afternoon and early evening is expected. A flooding risk will likely extend into Friday.

Much deeper and stronger forcing seems to develop in many models Saturday overnight as the main upper level trough axis moves east aloft. This could produce a concentration of heavier rainfall and some storms more so over Georgia and maybe extending west into NE Alabama. A risk for some flash flooding will likely continue on Friday afternoon into Friday night.

Models diverge on how amplified the upper level trough axis is Friday night into Saturday and into the weekend, which will have a big impact on whether the front shifts south of the area or not.

Model converge a bit more on stronger forcing and shear developing over the area on Monday. Shear is better with this system and instability is not bad. There may be some strong to severe thunderstorm threat with that system, but this is too far out in the extended to have much confidence with it.

AVIATION

(18Z TAFS) Issued at 1157 AM CDT Tue May 26 2026

Light rain showers will gradually increase in coverage through the afternoon and into the evening, with the potential for TSRA during the 20-00Z window. Have added a TEMPO at both terminals to reflect this higher confidence about TSRA and AWWs and/or amendments may be needed during this timeframe. Precipitation will wane this evening, but ceilings will drop to MVFR levels tonight and into Wednesday morning as low stratus builds back into the area.

HUN WATCHES/WARNINGS/ADVISORIES

AL...Flood Watch until 10 PM CDT this evening for ALZ006>010-016.

TN...None.