This accident occurred outside of our advisory area. However, conditions at the accident site are similar to those in the eastern reaches of our advisory area, near Marias Pass, and on the east side of Glacier National Park.
A party of three skiers planned to summit and ski Mount Lockhart (8691 feet) on the Rocky Mountain Front (Lewis and Clark National Forest). The peaks is just west of the Teton Pass ski area, which did not operate during the 2018-19 winter. They used snowmobiles to access the area, then ascended the peak's east ridge. On their descent, they worked down the peak's south ridge towards an east-facing bowl. While traversing the top of the bowl, one skier (Skier 2) triggered a slab 10-24 inches thick which released at the old snow-new snow interface. The debris carried him about 300 vertical feet before he stopped unhurt. The party regrouped and returned to the trailhead safely after the near-miss.
More details and the party's account of the incident under the "avalanche details" tab.
Skier caught and carried in Storm Slab avalanche, 4/13/19
A party of three skiers planned to summit and ski Mount Lockhart (8691 feet) on the Rocky Mountain Front (Lewis and Clark National Forest). The peaks is just west of the Teton Pass ski area, which did not operate during the 2018-19 winter. They used snowmobiles to access the area, then ascended the peak's east ridge. On their descent, they worked down the peak's south ridge towards an east-facing bowl. While traversing the top of the bowl, one skier triggered a slab 10-24 inches thick which released at the old snow-new snow interface. The debris carried him about 300 vertical feet before he stopped unhurt. The party regrouped and returned to the trailhead safely after the near-miss.
On April 9-10, the Mount Lockhart SNOTEL (6400 feet; 1.2 miles east-southeast) recorded 15 inches of snow and 1.7 inches of SWE equivalent. Air temperatures at the start of the storm were above freezing but cooled to the upper-20s before it ended. In the three days between the end of the storm and the accident, the station recorded daytime high in the upper 30s or low 40s and nightime lows in the mid to upper 20s. On the day of the accident, the party reported moderate to strong westerly winds. The SNOTEL recorded min/ max temperatures of 26 and 36 degrees, respectively.
Skier 1's account of the accident is below, slightly edited for clarity:
We encountered numerous areas of concern with regards to avy conditions. Travel was tedious at times, and we certainly crossed many slopes one at a time. Slopes lower down and more southerly aspects had significantly more strength and led us to believe that we always had options. We summited late, around 5pm, and all agreed that our original plans of a north aspect descent would not be OK. The new plan was to ski a familiar east-facing slope that was less steep and was also our shortest path back to the snowmobiles. Essentially, we all agreed to retreat in as safe a manner as we could find. I led down the initial summit ridge [the south ridge], and we all reconvened above the slope we intended to ski down. Skier 2 indicated he would like to ski another 100 yards further south to look around the corner and investigate additional terrain for better options. Upon skiing that 100 yards, he reached the steeper part of the open face and triggered a slide. Skier 3 and I saw the slide release from a safe spot. Within seconds it became apparent that our ski partner was kicking off his skis, but remaining on the surface. He was near the uppermost 5% of the debris flow and attempting to self-arrest. The debris continued past him, and he came to rest right about 300 feet below the trigger point, and just below the stauchwall. He was not at all buried or injured. One ski and both poles were near him. The other ski continued downhill with the debris another 400 feet or more.
Overall the slide was maybe 300 feet wide, had a 10-24 inch crown, and ran about 800 vertical feet. The debris did not set up hard, was slow moving, and did not produce a powder cloud. The slope angle where Skier 2 came to rest was less than 30 degrees. The estimated slope at the trigger point was 35-40 degrees. Another thing of note was that the terrain was very broad and open and the debris pile was 1-3 feet deep at most.
Additional details from email and phone conversations with the party iinvolved:
Skier 1 reported doing at least 10 hand pits to investigate the old snow- new snow interface on their ascent. "Everywhere we had dug up to this point the snow had come in warm and bonded well." The snow remained dry at upper elevations (above about 8000 feet) and the day felt cold. He described "crummy" snow conditions on north-facing terrain on their ascent; these slopes felt "hollow" and scoured, and they were able to break off small slabs 4-8 inches thick on skin track corners. By the time they reached the summit, the group had "a general feeling that conditions were not great." Skier 1 described the bed surface of the slide as a "hard melt-freeze crust." He reported that the slide released on a portion of the bowl that tilted slightly to the north. There may have been some drifted snow near the trigger point. Previous avalanche activity was limited to 2 small point releases below cornices that ran in the storm snow.
Skier 1 noted several contributing factors, including familiarity (all three had previiously skied in the area and Skier 1 had skied the bowl that slid), the lateness of the day, and the fact they had gleaned very little information about east facing slopes during the ascent and initial descent down the summit ridge.
All three skiers carried avalanche beacons, probes, and shovels. Skier 3 wore an avalung. All 3 skiers have completed a recreational Level 2 course in recent years. Skier 1 has some professional training.
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