2024/05/10 - Idaho - Donaldson Peak, Lost River Range

Published 2024/05/24 by Scott Savage and Ethan Davis - Sawtooth Avalanche Center

For much of the latter three weeks of April, the Lost River Range experienced unsettled but mostly dry weather punctuated with small storms. The first half of this period was warm, and the last half ended seasonably cool, with overnight temperatures well below freezing. The warm, sunny weather and some high-elevation rain produced a weathered, icy snow surface when it froze. This crust became the bed surface of the avalanche. 

Storms between April 25th and 27th brought 0.5” of snow water equivalent (SWE) to the Hilts Creek SNOTEL remote weather station 11.5 miles to the SE and 3,800’ below where the avalanche was triggered. Skiers visiting the area estimated 8-12” of snow fell during this time. Following the storm, temperatures dropped, creating a weak layer of facets above the firm icy crust below. Wind redistributed this snow into thin slabs on some slopes. 

On May 4th, six days before the accident, skiers encountered 4-10” thick isolated wind slabs. One group triggered a small 4-8” thick slab in the Fishbone Couloir near the top of Donaldson Peak. This avalanche released on an E aspect about 300’ to the south of the starting zone of the May 10th fatal slide. 

On May 5th, an intense storm brought 0.9” of SWE to the Hilts Creek weather station. Weather forecasts indicate that additional small disturbances likely brought smaller amounts of snowfall to the area through May 7th. This period's snowfall constituted most of the 12-18” thick slab observed at the avalanche crown. The slab failed on facets above an icy crust, the same layer described by skiers on May 4th.

On the nights of the 8th and 9th, temperatures remained above freezing at Hilts Creek. On May 9th, high temperatures reached 51 F, a twelve-degree increase from the day before. Similar temperatures were recorded at Hilts Creek at the time of the avalanche on May 10th. Later that afternoon, high temperatures climbed to 58 F. The combination of clear skies, light wind, and warm temperatures produced numerous naturally occurring slab and wet loose avalanches.

On the day of the accident, the party observed one recent natural slab avalanche on a west aspect on an adjacent ridgeline. Bare ridgelines and a significant amount of wind-loading were observed. Additionally, Skier 2 reported one snowpack collapse on a previously wind-loaded, west aspect at around 11,200’.

Early on Friday, May 10th, 2024, a party of two experienced backcountry skiers set out from Jones Creek, approximately 9 miles northwest of Mackay, Idaho (Fig. 1). They ascended the west face of Donaldson Peak, traveling by foot, skis and skins, and crampons. After reaching the summit, they began downclimbing the NE ridge of Donaldson, using crampons, as they moved toward their planned north-facing ski descent. While downclimbing a steep snow gully on the E side of the ridge, Skier 1 triggered and was caught in a slab avalanche. He was unable to self-arrest with crampons and his ice axe. He was carried downhill, out of sight of Skier 2. 

Skier 2 immediately moved downslope, where she could better see the avalanche and debris. She could not see Skier 1. She hit the SOS button on her inReach device (11:55 AM), transitioned from crampons to skis, and descended the slope to perform a transceiver search. She received an initial transceiver reading of 70m, lost the signal while continuing downhill, and did not regain distant signal until the toe of the debris. She followed the signal uphill, received a lowest reading of 1.8m, and probed to locate Skier 1. She dug to extricate Skier 1, initially uncovering a hard ice chunk she had probed near Skier 1’s boot. Skier 1 was unconscious and not breathing when fully extricated. After Skier 2 performed a few rounds of CPR, approximately 1 hour had elapsed since the avalanche. She continued CPR for approximately 3 hours until Skier 1 was evacuated via helicopter. Skier 1 was carried about 1,100 vertical feet and did not survive the 5 foot deep burial. He did not appear to incur significant trauma while being carried downhill.

Avalanche accidents are traumatic events that have lasting consequences for all involved. Our deepest condolences go out to everyone who has been affected by this event. We offer these thoughts with the hope of helping to avoid future accidents. We in no way intend to place blame.

Solar Radiation/Warming: The day of the accident was clear with intense sun. Several significant slab avalanches – in addition to loose wet avalanches – occurred. The fatal avalanche did not appear to be a wet slab avalanche, and the bed surface was hard and icy. Our current understanding of the role of solar radiation on snow stability is that neither sun nor heat is typically the primary factor driving dry snow, slab avalanche activity. However, anecdotal evidence and professional observations indicate that, on rare occasions, intense sunshine can alter the slab character enough to increase the chance of natural or human-triggered, dry slab avalanches. 

Deep Burials: This group was equipped with the standard avalanche and ski-mountaineering safety and rescue gear, including transceivers, probes, shovels, and satellite communication devices. They were highly trained and practiced. Despite this, the rescue was not successful. Deep burials increase the extrication time, decreasing the chance of survival. Additionally, the chance of successful rescue is about 5 times lower for victims buried over 4 feet deep versus those buried less than 1.3 feet deep, independent of burial duration (Procter et al, 2016). Statistically, Skier 1’s burial depth of 5 feet made survival highly unlikely.

Airbag/Backpack: The victim was not wearing an airbag pack. Research and evidence indicate that in some situations a deployed airbag can reduce human burial depth. That said, airbag packs’ weight and limited capacity/utility are limitations that may preclude their use on many ski-mountaineering missions.

Travel Mode: When he triggered the avalanche, the victim was traveling by foot, carrying his skis on his backpack. Getting caught in an avalanche while traveling on foot or while skinning dramatically reduces the odds of escaping. 

Pre-trip Planning: Although the Lost River Range is a popular springtime ski mountaineering destination, public avalanche, snowpack, and weather information is very limited. It is outside any avalanche center’s forecasting area. The nearest avalanche center forecast zone is 20-25 miles SW in the Pioneer Mtns which can have a very different snowpack. The Sawtooth AC was closed for the season, issuing a final product for the Pioneer’s on May 3rd. 

Persistent Weak Layers in Spring: The fatal avalanche released on a layer of faceted snow above a crust. The weak layer and bed surface formed in late April and May. While faceted layers form more frequently in the colder winter months, the springtime snowpack in high elevation locations like the Lost River Range can “lag” the snowpack of neighboring, lower elevation mountain ranges; meaning that faceted layers can form or persist weeks or months later in the season. In this accident, the skiers were aware of the weak layer and had been tracking it through recent visits, and in conversations with others who were skiing in the Lost River and neighboring ranges.

Electromagnetic Interference (EMI): There is no way to know if EMI was a complicating factor in losing the initial signal. Following these guidelines will help limit the effects of EMI during a transceiver search.

Note:

USFS Sawtooth Avalanche Center (SAC) staff did not visit the accident site. Details are based on interviews with the surviving party member, conversations with others who skied in the area before the accident, and a detailed account compiled by Ben VandenBos. You can read Ben’s observations and account here.