textproduct: Huntsville

KEY MESSAGES

Issued at 152 PM CDT Wed May 20 2026

- Medium to high chances (60-90%) of showers and thunderstorms are forecast today through early next week. No severe weather is forecast.

- Locally heavy downpours and frequent lightning may accompany all thunderstorms and those with outdoors plans or events should monitor the forecast.

NEAR TERM

(Rest of Today and Tonight) Issued at 152 PM CDT Wed May 20 2026

The approaching surface front has slowly moved east today and currently stretches from southeastern Ohio through the Nashville, TN area into NW Alabama. Forcing along and ahead of this feature is producing an area of scattered showers and thunderstorms. Shear is not very impressive. 2-6 km and mid level lapse rates are not too impressive (2-6 km only 6 to 6.5 degrees/km). DCAPE values are still very meager (only 300 to 600 J/kg). However, SBCAPE has increased to between 1000 and 2500 J/KG and low level lapse rates are around -8 in SPC analysis. Thus, some stronger storms producing downburst winds between 30 and 55 mph cannot be ruled out this afternoon. However, given weak nature of 0-3 km shear, not expecting an area of organized severe thunderstorm development. The Storm Prediction Center has placed the area under a mesoscale discussion for a possbile severe thunderstorm watch, but this is very unlikely (only 20% chance or less of a watch). Frequent lightning, heavy downpours and some small hail cannot be ruled out in the strongest storms.

It looks like strongest and most persistent forcing will remain mostly in Tennessee NE into the southern Ohio Valley. One quarter to around half an inch in southern middle Tennessee looks reasonable for rainfall amounts through tonight. The majority of guidance pushes the front south of the Tennessee River late tonight into the daybreak on Thursday. We should lose instability overnight behind the front. Some post-frontal forcing will likely produce some lingering light to moderate rain over the area.

SHORT TERM

(Thursday through Saturday) Issued at 1120 AM CDT Wed May 20 2026

During the day on Thursday, guidance pushes the front back to the northwest. Shear remains weak near and along this frontal boundary. Instability is forecast to again climb into the 1000 to 2000 J/KG range, maybe slightly higher. Again lapse rates and DCAPE values look fairly meager. Overall forcing should be better, but severe thunderstorms do not look possible. General to strong thunderstorm activity is likely though producing frequent lightning, heavy downpours, and gusty winds to around 45 mph.

The frontal boundary continues to more quickly move northward Thursday night into the day on Friday. At the same time, models form a pre-frontal trough axis that extends WSW from the Mid- Atlantic through northern Georgia into central Mississippi. 30 knots of 0-3 km shear is forecast by several models by the late afternoon into the early evening hours along this feature. SBCAPE values climb in the afternoon into the 1000 to 2500 J/KG range in several models. Luckily, lapse rates look fairly poor (5.0 to 6.0 degrees/km). DCAPE values remain less than 500 J/kg as well. All in all, there may be just enough shear for a low end organized severe thunderstorm threat producing damaging winds. Some enhanced forcing associated with an upper level disturbance moving along the pre-frontal trough axis could provide the spark for a more organized cluster of storms along with the minimal shear. Given forcing and high PWAT values between 1.5 and 1.7 inches, this could produce between 0.5 and 1.0 inches of additional rainfall over the area. Some locally heavier amounts can't be ruled out given forcing and some possible brief training of storms.

This pre-frontal trough axis doesn't move much Friday night into Saturday. However, we may have a slight break from heavier rainfall. The base of the shortwave trough axis looks too far south for much convection to develop despite a good amount of instability developing in the afternoon. It looks like we will be under the influence of more subsidence. However, widespread cloud cover and maybe some showers will likely keep highs in the upper 70s to lower 80s.

LONG TERM

(Saturday night through Wednesday) Issued at 1120 AM CDT Wed May 20 2026

The position of the pre-frontal trough axis changes little through early next week. Occasional disturbances continue to move east across it at times throughout that period. Instability builds each day in the afternoon to between 1000 and 3000 J/KG. Not seeing shear increase, but flooding will likely become an issue if it already isn't by the weekend. At this time, it looks like there is enough of a break given the primarily diurnal nature of the convection to keep a more serious flash flooding/flooding threat from materializing. However, some low end flash flooding or minor river flooding is not out of the question through that period. Overall, daytime highs will remain below normal (upper 70s/lower 80s) due to cloud cover and afternoon convection. Overnight lows will remain fairly warm and humid only dropping into the lower to mid 60s.

AVIATION

(18Z TAFS) Issued at 152 PM CDT Wed May 20 2026

Mainly VFR conditions are expected through 21Z at both terminals. A PROB30 for more isolated to scattered -TSRA impacting either terminal has been included in the current TAF package. MVFR CIGS or VSBYS are expected within that PROB30 grouping. Expecting more persistent -SHRA after 21Z at both terminals. A tempo for -TSRA was included at both terminals between 20/21Z and 21/01Z. MVFR CIGS/VSBYS chances are higher then. After 2Z at KMSL MVFR CIGS will continue. A prob30 group was included to account for scattered -TSRA potential between 2Z and 6Z for MVFR CIGS/VSBYS.

HUN WATCHES/WARNINGS/ADVISORIES

AL...None. TN...None.