CAIC

Avalanche Details

Location: Commodore Basin, north of Red Mountain Pass
State: Colorado
Date: 2024/02/18
Time: Unknown
Summary Description: 1 backcountry ski guide caught, partially buried, 1 client caught and buried
Primary Activity: Human Powered Guiding Client
Primary Travel Mode: Ski
Location Setting: Backcountry

Number

Caught: 2
Partially Buried, Non-Critical: 0
Partially Buried, Critical: 1
Fully Buried: 1
Injured: 0
Killed: 0

Avalanche

Type: HS
Trigger: AS - Skier
Trigger (subcode): u - An unintentional release
Size - Relative to Path: R2
Size - Destructive Force: D2
Sliding Surface: O - Within Old Snow

Site

Slope Aspect: E
Site Elevation: 11500 ft
Slope Angle: 42 °
Slope Characteristic: Convex Slope,Sparse Trees,Gully/Couloir

Avalanche Comments

The avalanche occurred near treeline on an east-facing slope in Commodore Basin, north of Red Mountain Pass. It was a hard slab avalanche unintentionally triggered by a backcountry skier. It was small relative to the path and produced enough destructive force to bury, injure, or kill a person. It broke on a layer of old, faceted snow (HS-ASu-R2-D2-O). The weak layer was near-surface faceted crystals that formed in early February. The avalanche began in an area where the weak layer was 1 foot below the snow surface. The avalanche propagated across a northeast-facing portion of the slope and broke up to 3 feet deep. The avalanche was around 250 feet wide. It ran approximately 550 vertical feet through a shallow gully.

The avalanche ran in the old snow and failed on a weak layer of near-surface faceted crystals buried in early February. The crown began in an area where the weak layer was 12 inches from the surface and propagated to a northeast-facing slope, and that was where the crown face was three feet deep. Some of the debris ran into a small gully feature, and the remainder fanned out in the flatter area below.

Backcountry Avalanche Forecast

The Colorado Avalanche Information Center’s (CAIC) forecast for the area around Red Mountain Pass for February 18, 2024, rated the avalanche danger at MODERATE (Level 2 of 5) at all elevations. The primary problem was Persistent Slab avalanches on all aspects above treeline, and west through northwest to southeast near and below treeline. The likelihood was Possible, and the expected size was Small to Large (up to D2). The second problem was Wind Slab avalanches above treeline from west through northwest to southeast. The summary statement read:

If you find the shallow area of the slope where it is easier to impact weak, collapsible snow layers, you could trigger a large, dangerous avalanche. Likely trigger spots exists near shallowly buried rocks, on steep rollovers, and below ridges and cliffs. Avalanches will be larger on wind-drifted northerly and easterly-facing slopes, and can step down to weak layers in the middle or bottom of the snowpack. Use caution on steeper slopes if the snow surface transitions from soft to stiff, or in places with a rounded or wave-like appearance. Don’t place too much faith in a stiff-over-weak structure, and odds are you’ll observe no warning signs before the slope fails.

Safer riding options exists on low-angled, wind-sheltered slopes without steep overhead hazard.

Snowpack Summary

The snowpack in Commodore Basin developed from small to medium-sized storms punctuated by long periods of no precipitation. Late January was dry and cold, and the snowpack surface faceted. Intermittent storms began on February 2. By February 18, CAIC forecasters measured a total accumulation of 57 inches of snow and 4.6 inches of snow water equivalent at the Red Mountain Pass study plot, about 0.25 miles south of the incident site. Six to nine inches of snow fell in the week before the avalanche. Moderate westerly winds drifted snow.

Light intensity snow was falling on February 18, 2024. Winds were light to moderate from the west. The daytime high temperature was 27 F.

Events Leading to the Avalanche

This was a guided group of backcountry skiers, with one guide and five clients. The group made two ski descents in the upper basin. They were skiing down Commodore Basin to Highway 550 to end their ski tour. The Commodore Basin area is popular with backcountry recreationists and was heavily traveled on the day of the incident. The group chose a slope that had fewer tracks and planned to descend one at a time.

Skier 1, the guide, traveled halfway down the slope and stopped in a sparse group of trees on the skier’s right side of the slope. Skier 2 began their descent and triggered the avalanche on their “second or third” turn. The avalanche caught Skier 2 and carried them approximately 500 feet downslope through trees and over a small rock band. When the avalanche stopped, Skier 2 was fully buried near the toe of the debris. The avalanche engulfed Skier 1 as it swept down the slope. Skier 1 was carried approximately 150 feet and was buried with just one hand out of the snow (partially buried-critical). Both skiers were buried near the snow surface and in relatively soft snow. They were able to clear the snow from around their faces.

The remaining four members of the group began an avalanche transceiver search but saw the two skiers. Skier 1 dug themselves free of the debris. The group helped free Skier 2. Neither were injured. They lost one ski and several ski poles in the avalanche. The group made its way back to Highway 550.

Comments

We do our best to describe avalanche involvements to help the recreational community better understand factors that may have contributed to the outcome. We offer these comments in the hope that they will help people avoid future close calls. It is hard to admit mistakes and expose oneself to criticism. This group's willingness to do so is important in helping the community learn collectively.

In this case, the group changed their plans due to the intense backcountry use in the area that day. They looked for a slope with no other tracks. They chose a steeper slope not often traveled on a slightly different aspect than they initially planned.

They saw a small avalanche on a slope adjacent to the one they planned to ski. They thought it ran within the past day. Recent avalanche activity is an obvious sign of unstable snow and a clue to avoid traveling on similar slopes.

Skier 1 stopped in a spot that was not far enough out of the avalanche track and was overrun by the avalanche. The group underestimated the potential size of a triggered avalanche on the slope. A characteristic of the Persistent Slab avalanche problem is that avalanches can break wider and further than expected. They require a wider margin of safety than avalanche problems like Storm Slab or Wind Slab avalanches.

Skiing one at a time reduces the groups' exposure to avalanche hazard and allows the allocation of resources; in this case, there were four rescuers in a position to aid the buried skiers.

The group had tackled a significant ski objective earlier in the day and was exiting the backcountry. After achieving your goal, it is important to recognize that you may still be navigating avalanche terrain and manage that terrain and avalanche problems appropriately.