CAIC: Colorado Avalanche Information Center

2012/01/22 - Colorado - Trestle Trees, Winter Park

Published 2012/01/31 by Spencer Logan - Forecaster, CAIC


Avalanche Details

  • Location: Trestle Trees, Winter Park
  • State: Colorado
  • Date: 2012/01/22
  • Time: Unknown
  • Summary Description: 1 inbounds skier caught, buried, and killed
  • Primary Activity: Inbounds Rider
  • Primary Travel Mode: Ski
  • Location Setting: Ski Area - open area

Number

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

Avalanche

  • Type: SS
  • 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: N
  • Site Elevation: 10400 ft
  • Slope Angle: 45 °
  • Slope Characteristic: --

Avalanche Comments

This was a small avalanche. The starting zone was a rocky outcrop with slope angles between 40 and 60 degrees. The main portion of the avalanche, on the rocky outcrop, was about 40 feet wide. The left (west) side of the avalanche extended for another 40 feet, but ran less than 30 vertical feet. On the flanks, the snow just above the rock was very weak and consisted of large chains of depth hoar. Two recent storms had formed a very soft storm slab in the upper third of the snowpack. In snowpack tests, the columns would first break in the upper portion of the facets, and then fail to the ground as the facets at the ground collapsed. In the surrounding area, investigators found many short shooting cracks, less than 2 meters, and very small collapses.

Weather Summary

December and the first half of January were very dry. Below treeline the shallow snowpack completely faceted during this period. On January 17, Winter Park reported 7.5 inches of snow. Another 7 inches fell from January 20-22. Strong winds accompanied both storms, but the avalanche site was wind sheltered and the snowpack showed little evidence of wind.

Snowpack Summary

The snowpack below treeline was very thin. Two soft layers of recent storm snow capped well-developed facets and depth hoar. Boot penetration was to the ground, and ski penetration was little better.

Events Leading to the Avalanche

Skier 1 left his party mid-afternoon on January 22. The plan was to meet up for lunch at the car after one run.

Accident Summary

We believe Skier 1 followed a traverse into the Trestle Trees. The area had seen some ski traffic, including ski patrollers. Skier 1 cut along low angel terrain below a short, very steep rock outcrop. He probably triggered the avalanche from below. Slight terrain features funneled the majority of the avalanche towards Skier 1. The avalanche caught Skier 1 from the side and behind, and knocked him over. He was fully buried two to three feet deep, face downhill, with one had reaching towards the surface.

Rescue Summary

Skier 1's party notified Winter Park Ski Patrol when he did not return after the lifts closed. Searchers worked through the glade by headlamp. Searchers spotted the avalanche debris and began hasty probing while the rest of the search party converged. One of the searchers uncovered Skier 1's glove while probing.

Comments

This avalanche involved a small terrain trap. The steep rock face transitioned to lower angled slopes. A downed tree below the outcrop funneled a portion of the avalanche towards Skier 1's location. Avalanche debris was able to pile up deeply, for the volume, where he was caught. The avalanche may not have buried Skier 1 if he had been caught in other portions of the debris. Skier 1 may not have been buried, or even triggered the avalanche, if he had been traveling 10 feet further down hill, away from the rocky outcrop.

Small avalanches have killed 10 people in Colorado since 1991. Roof avalanches have killed three people, and all ran a shorter vertical distance than the avalanche at Winter Park. Most of the other small avalanches have involved terrain traps, and often a solo traveler or one separated from the rest of the party. A small fatal avalanche occurred a few days before, on January 18 in the backcountry near Snowmass, and ran 30 vertical feet.

This was the second avalanche in Colorado since 1991 to kill a skier in clearly open terrain within a ski area boundary. A large wet avalanche killed a skier at Arapahoe Basin on May 30, 2005. Several other fatalities occurred in terrain ski patrol temporarily or permanently closed.

Media

Images

Snowpits

Image Missing
Figure 5: Snow profile gathered on January 23 from the right flank of the avalanche, on the rocky outcrop.