2018/02/17 - Montana - Canyon Creek, Whitefish Range

Published 2018/06/15 by Zach Guy - Director, FAC

A steady flow of Pacific storms built an above-average snowpack of 8 feet deep by early February in the Big Mountain area.   On February 8th, a rain event to approximately 6,000’ formed a pronounced rain crust on the snow surface.  A cold front on the same day deposited 2” of low-density snow over the crust.  The snow surface subsequently metamorphosed into a layer of near surface facets during the six days of dry weather that followed.  On February 14th, this crust/facet layer was buried by a series of relatively low density snowfall events that began to build a cohesive slab of storm snow.  At the Big Mountain Summit Station, 8” of snow accumulated with the first pulse of snowfall on February 14th.  This storm produced a small, natural storm slab cycle in adjacent mountain ranges that saw slightly higher snow totals.  The storm on February 17th thickened settled storm totals to 13” by 3 p.m and 22” (2.9” SWE) by the end of the storm that night. This formed a soft slab of new snow over the faceted rain crust at mid and low elevations.  The Flathead Avalanche Center issued an avalanche warning on February 17th and rated the avalanche danger Considerable rising to High by that night.  The storm produced very heavy snowfall rates on the afternoon/evening of the 17th, resulting in an unstable snowpack structure that produced numerous natural soft slab and loose snow avalanches up to D2 in size.  These ran on the buried rain crust or on mid-storm layers throughout the advisory area.

On the afternoon of February 17th, 2018, Skier 1 was skiing alone near Kona, a lift accessed backcountry area east of Whitefish Mountain Resort in the Canyon Creek drainage in the Whitefish Range.  Around 2 p.m., Skier 1 text messaged his wife that he was finishing his 2nd lap, and would be returning by 3:30 p.m after one more lap.  Skier 1 was traveling solo; thus we have no firsthand accounts of the events leading to the accident.  Skier 1 was carrying a handheld global positioning system (GPS), which was later recovered and used to track his movements leading up to the accident.  Skier 1’s GPS track shows his first two laps on moderately angled terrain in the Kona area, stacking his tracks near to each other and ascending on the same skin track to the Kona ridgeline. On his final lap, he descended a short, steep pitch below Kona Point and traversed a bench to the Beaver Pond. From there, he descended the skier’s right side of a steep gully that drains towards Canyon Creek.  Skier 1’s track enters the steepest part of the terrain halfway down the slope.

Skier 1 was traveling solo; we have no first-hand accounts of the accident.  Skier 1 was found without evidence of physical trauma, with one ski attached and the other released but contacting his boot.  The rest of his gear was intact and in place. He was face-down oriented facing downhill. His location was approximately 250 vertical feet downhill and in a terrain feature skier’s left of the crown line of Avalanche A.  Based on the burial characteristics, it appears that Skier 1 was caught and buried by a relatively small avalanche (Avalanche B). It is unknown whether Avalanche B was connected to Avalanche A or two separate avalanches. We hypothesize that Skier 1 triggered Avalanche A and was skiing away from the avalanche when he was caught by Avalanche B, which may have been a sympathetic or secondary release.  

On the evening of February 17th, family members of Skier 1 became concerned with his whereabouts, when he had not communicated or returned to his parked car at the base of the ski area.  At 7:17 p.m., they called 911, initiating a search and rescue response.  A hasty team of four searchers used over-the-snow vehicles to gain access the area, but aborted search efforts due to blizzard conditions and mechanical issues.  On February 18th, under challenging weather and snowpack conditions, a team of 11 made up of SAR members, an FAC forecaster, and volunteers conducted a targeted beacon and visual search of the Kona area while Two Bear Air flew over the site (Figure 7).  Ground teams identified and traced Skier 1’s tracks from his first two laps, but heavy snowfall and winds had concealed much of the visual evidence, including the start of his third lap.  On February 19th, and expanding party of searchers located the crown and debris of Avalanche A with a faint track entering the slope. They conducted spot probing and beacon searches in pockets of deeper debris and in tree wells.  Search teams returned in subsequent days to conduct probe line searches, Recco search, and a canine search of the debris from Avalanche A, with no hits.  Systematic search efforts in the Kona area and surrounding backcountry continued for the next week, gridding the area, probing tree wells, and searching with beacons and Recco. The snow conditions were too deep for effective canine searching. On February 25th, after thousands of volunteer and professional search hours, the large scale search was suspended until spring melt made for more productive searching conditions.  Organized searching resumed on May 10th.   On May 12th, a team of 4 canines were deployed, and at 10:58 a.m., a search dog located Skier 1 buried beneath 2 feet of snow.  The entire search involved 90 personnel from organizations including Flathead SAR, North Valley SAR, Flathead Nordic Patrol, CAN-AM SAR, Lewis and Clark SAR, Gallatin County SAR, the US Forest Service, the Flathead County Sheriff’s office, the Flathead Avalanche Center, and Two Bear Air, as well as 77 civilian volunteers. 

Skier 1 was likely caught in a storm slab avalanche.  This type of soft slab avalanche is most unstable during or shortly after rapid loading events.  The FAC had issued an avalanche warning on February 17th; human triggered and natural avalanche activity is more likely when the avalanche danger is rated Considerable or High.   The instability in this case was most pronounced where the storm snow accumulated over a rain crust below approximately 6,000’.  Before descending to an elevation where the rain crust was lurking, Skier 1 traveled on several steep slopes at higher elevations where this touchy structure did not exist. This complication may have led to an increased sense of confidence in the snowpack leading to the accident.  Storm slab avalanches most commonly fail on slopes steeper than 35 degrees. The terrain at the accident site rolls over steeply to slope angles of 40 degrees.  

Skier 1 was familiar with the terrain in this area and had advanced backcountry travel skills. He was carrying rescue gear and wearing a transmitting beacon.  He followed good protocol in communicating his travel plans to others.  Unfortunately, traveling without a partner eliminated any chance of quick companion rescue. In most avalanche fatalities, asphyxiation occurs within the first 15 minutes of burial; timely rescue is critical.  The avalanche, which appears to be relatively small, was exacerbated by the shape of the terrain.  Gullies funnel avalanches into unusually deep debris piles relative to open, planar slopes.  Search efforts focused on the obvious avalanche debris below the crown line of Avalanche A, but unfortunately, overlooked the adjacent terrain feature which acted as a terrain trap.