EF1 tornado in Teton County, Wyoming

On 10/15/25 from 1:35 to 1:37 PM MDT, a thunderstorm produced an EF1 tornado near Alta, WY in the Teton Canyon portion of the Caribou-Targhee National Forest. Reports from social media after the event mentioned tree damage in the Teton Canyon area. Later drone footage taken by the local sheriff's office during the week after this event, as well as satellite imagery, identified a swath of tree damage consistent with 87-104 mph winds (EF1).

Wind speed was determined using the Enhanced Fujita Scale Damage Indicator for #28 'Tree - Softwood', since this tornado occurred in a dense coniferous portion of the Caribou-Targhee National Forest. No structures were in the path. Aerial drone photography showed hundreds of trees blown down by the tornado, with a clear damage swath/path through the forest. A majority of trees in the path were uprooted (Degree of Damage 3, 87 mph) or had their trunks snapped (DoD 4, 104 mph). Bark was visible on trees, and there was no notable debarking or stripping of branches seen in imagery (DoD 5). Given relatively healthy trees with no reason to believe trees were stronger or weaker than average, the lower and upper bounds for the DoDs were not utilized, and expected values were referenced. This led to a wind speed estimate of 87 to 104 mph, which is rated EF1 on the Enhanced Fujita Scale.

The tornado damage path is approximately 1.0 miles long, with a maximum width of 125 yards. The tornado damage path started at an elevation of 7900 ft ASL and ended around 6900 ft.

A longwave upper-level trough was positioned over the Intermountain West upstream of an amplified ridge that had its axis over the Great Plains. Southerly flow ahead of the trough brought anomalously high atmospheric moisture to western Wyoming, sourced from both the Pacific Ocean and Gulf of Mexico. CAPE values in the Alta, WY area were in the 200 to 400 J/kg range with 0-6 km shear in the 50 to 60 kt range. In the 30 minutes prior to producing this tornado, the parent thunderstorm moved across the Teton Basin between Driggs, ID and Victor, ID producing pea-sized to nickel-sized hail. One strong thunderstorm embedded in a line of storms produced an EF1 tornado near Alta, Wyoming in the Caribou-Targhee National Forest. Several trees had to be cut and cleared from forest service access roads.

This is the 3rd confirmed tornado in Teton County history (1987 and 2022 each had 1 as well). It is also the latest tornado (warm-season-wise, and calendar-year-wise) recorded in Wyoming history, with only 1 other recorded tornado in October (10/7/1969 in Goshen County). As of Dec 2025, November through March have no reported tornados in Wyoming.