A Rock Springs man died Saturday after an avalanche buried his snowmobile in the Wyoming Range near the Horse Creek Trail.
“This is the first avalanche fatality anywhere in the U.S.” this winter, Bridger-Teton Avalanche Center Director Bob Comey said.
Sublette County Coroner Curtis Covill identified the man as Dustin LaPant. The 31-year-old rolled his snowmobile a couple of miles away from the Blind Bull Summit warming shelter, Comey said, about 1,000 feet off the popular Horse Creek Trail, which is a groomed track.
LaPant was riding uphill on a small convex slope when a wind slab fractured on a buried layer of faceted snow. The 100-foot-wide avalanche had a 22-inch crown and ran roughly 100 feet. It broke above LaPant, carrying him about 50 feet and flipping his snowmobile on top of him.
“He was pinned underneath his sled; his head was about a foot underneath the snow,” Comey said.
LaPant’s partner was unable to rescue him after the slope broke around 10 a.m., so he remained under the snow for about an hour before another rider came along and was able to dig out his face at about 11 a.m.
“By that time, he was cold and unresponsive,” Comey said.
According to 2012 research published by the Canadian Medical Association Journal, avalanche victims who are buried for an hour have just over a 20 percent chance of survival.
Neither Comey nor Sublette County sheriff’s Sgt. Travis Bingham could say why LaPant’s partner was unable to rescue him. Comey called the terrain around the slide “difficult to navigate if you don’t know how to ride a sled off trail,” and said the possibility of a second slide during the rescue may have kept the partner from springing into action.
“A lot of things went against their luck to get him,” Bingham said.
After it became apparent that LaPant had died in the avalanche, Tip Top Search and Rescue retrieved his body from the debris about 13 to 15 miles from the Sherman Guard Station trailhead.
“It took a while to get the team in,” Bingham said.
Comey said a multitude of factors converged to create the fatal conditions of the slide. The Wyoming Range’s shallow snowpack — the snow depth was about 3 feet at the site of the slide — allowed facets to form, and a stiff wind slab that formed over the past eight or nine days sat atop the buried weak layer.
The convex shape and short run of the slope also contributed to LaPant’s burial, creating a terrain trap. The trigger point of the slide, Comey said, was 37 degrees, close to the most common slope angle found in avalanche events, while the top of the slope was between 32 and 35 degrees.
Those factors, along with the weight of a snowmobile plus a rider, combined to trigger an avalanche on a persistent weak layer that hadn’t caused many slides in the past few weeks.
“It was kind of a perfect storm,” Comey said.