A father and son were snowmobiling just north of Ant Knolls. The father became stuck in a small bowl low on the slope. When his son attempted to help, he also became stuck nearby. An avalanche released, catching and carrying the father while narrowly missing the son. The father and his snowmobile were carried approximately 300 feet downhill. He came to rest against a tree and was buried under about two feet of snow. The son immediately began searching for his father and called 911, which connected him with a Wasatch County Search and Rescue team member who walked him through how to use his transceiver. He was able to locate his father and partially unbury him, but sadly, his father had passed. Wasatch County Search and Rescue team members arrived on scene and transported both the father and son off the mountain.
The terrain where the avalanche occurred is east-northeast facing with slope angles between 33 and 40 degrees. The riders were about 400 vertical feet below the ridgeline in a small bowl feature when the avalanche occurred. It is possible a collapse propagated uphill from their location, triggering a large, soft-slab avalanche from above. The area is very exposed to wind loading, and the upper part of the slab was much thicker than the lower part. The slab traveled about 700 vertical feet downhill and left semi-soft deposition piled about 2-8 feet deep.
The crown of the avalanche was just to the east side of the north ridge from Ant Knolls, around 9400'. The wind-drifted soft slab was about 2.5 feet thick, sitting atop weak, faceted snow.
Approximately half the height of the snowpit was new snow from 2/17-2/18.
The slab was very connected and, lower down the slope, wrapped around a subtle aspect change and pulled out more snow out of sight to the looker's left.
The father was seemingly stuck in this lower bowl below the steeper slope above when the avalanche occurred.
The father was caught and carried by the avalanche and came to rest by the small fir tree in the middle of the photo under a few feet of snow.
The Ant Knolls area has steep terrain facing many aspects, with low-angle terrain below.
The coordinates of the avalanche crown were approximately: 40.55805, -111.57710.
The red X marks the approximate burial location.
The Ant Knolls area is easily accessible via the Snake Creek trailhead outside Midway, UT. The red pin marks the crown of the avalanche.
This photo illustrates the approximate boundaries of the avalanche, including the crown where the slab released, the flanks marking the sides of the path, and the debris field in the runout zone.
In the weeks leading up to the accident, Utah was experiencing one of its driest winters on record. Snow cover was shallow and largely limited to shady upper- and mid-elevation terrain. An early January storm delivered 18–24 inches of snow, with about 1.25 inches of snow water equivalent (SWE), across the area. After that, the skies remained clear for several weeks. During this prolonged dry spell, the surface snow became weak and faceted, creating a fragile snowpack structure. On February 11–12, the Central Wasatch received about 10- 12 inches of snow with 1 inch of SWE. While this improved riding conditions, it also highlighted just how unstable the snowpack had become, with numerous human-triggered and remotely triggered avalanches reported. Beginning Monday, February 16, the Utah Avalanche Center issued an Avalanche Watch ahead of a powerful series of storms forecasted to impact the state. The Watch remained in effect through February 17. On February 18, the UAC escalated to an Avalanche Warning for very dangerous backcountry conditions, urging people to avoid avalanche terrain. The storm cycle was significant. By the time of the accident, the mountains had received approximately 2 feet of snow, with 2–2.5 inches of SWE. Winds blowing from the south and west were very strong in the days before the accident, with gusts reaching 80 mph.
The accident occurred on the afternoon of 2/18 when the storm was producing heavy snowfall and moderate to strong winds.
The winds on the days leading up to the avalanche were primarily out of the south and west.
Winds were very strong on Monday, 2/16, before the storm arrived. They subsided on Tuesday, 2/17, but picked back up again on Wednesday, 2/18.
The storm ushered in some of the coldest temperatures of the season, beginning on Wednesday, 2/18, at midday.
The avalanche failed at the top of our Dry January Layer (DJL), a thick, weak layer of facets that developed at the surface during the extended January dry spell. These were about 2-3 mm, well-developed facets. We noted that much of the "body" of the slab was due to the pre-Valentine's snowstorm, which added about 1" of SWE on top of the faceted surface snow. Warm temperatures followed that storm, making the layer denser. The slab was relatively soft, composed of F-hardness snow over 4F, over a 1F layer resting above the pre–Valentine’s interface. While not particularly hard, the slab was cohesive and well connected—stiff enough to transmit stress and possibly allow a trigger from roughly 400 feet downslope.
UAC Director Paige Pagnucco and UAC Avalanche Forecaster Trent Meisenheimer visited the accident site on Thursday, 2/19, along with Wasatch Country SAR members, who were retrieving the father's snowmobile. From the estimated point of the father's stuck sled, the propagation distance was about 400 vertical feet uphill, highlighting the slab's connected nature. The avalanche failed on a weak layer of facets that formed during the January dry spell. The avalanche danger for that area was rated HIGH that day with an Avalanche Warning in place.
At the Utah Avalanche Center, we strive to learn from every avalanche incident and share insights to help others avoid similar accidents. We have all experienced close calls and understand how easily mistakes can happen. Our goal with this report is to provide a valuable learning opportunity, and we all aim to learn from accidents like this, without in any way pointing fingers at victims. Thank you to Wasatch County Search and Rescue and the Wasatch County Sheriff's Office for providing closure to this individual's family and friends.
Our heartfelt condolences go out to the victim's family, friends, and all those in the community affected by his loss.
