CAIC

Avalanche Details

Location: Greg Mace Peak, south of Ashcroft
State: Colorado
Date: 2022/10/27
Time: 8:50 AM
Summary Description: 1 backcountry skier caught
Primary Activity: Backcountry Tourer
Primary Travel Mode: Ski
Location Setting: Backcountry

Number

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

Avalanche

Type: SS
Trigger: AS - Skier
Trigger (subcode): u - An unintentional release
Size - Relative to Path: R1
Size - Destructive Force: D2
Sliding Surface: G - At Ground/Ice/Firm

Site

Slope Aspect: N
Site Elevation: 12450 ft
Slope Angle: 42 °
Slope Characteristic: Gully/Couloir

Avalanche Comments

This was a soft slab avalanche unintentionally triggered by a backcountry skier. It was small in size relative to the path and produced enough destructive force to bury, injure, or kill a person. The avalanche released at the ground (SS-ASu-R1-D2-G). The avalanche broke about 60 feet across the slope, ran 1200 vertical feet, and started on a 42-degree, north-facing couloir above the treeline.

Backcountry Avalanche Forecast

This avalanche occurred before the Colorado Avalanche Information Center (CAIC) was issuing daily avalanche forecasts for the 2022-23 season. The CAIC updated the Statewide Avalanche information on October 27, 2022. The Statewide read:

We received our first significant snowfall of the season between late Saturday and Thursday morning. Storm totals range from 6 to 14 inches in the San Juan Mountains, 12 to 24+ inches over much of the Central Mountains, and 5 to 12 inches across the Northern Mountains, though portions of the Flat Top Mountains did even better than that.

We now have over a foot of settled snow on the ground in many locations. This is enough snow to drift and obscure the ground cover. This means we need to start taking the threat from avalanches seriously. Once snow piles up or drifts deep enough to obscure the ground cover avalanches are possible. This doesn't take much on grassy slopes or steep rock slabs.

It's very early season. The only slopes with enough coverage to slide on will also be the most dangerous. Look for and avoid steep slopes with stiffer wind-drifted snow. Even a ride in a small avalanche can end your season early, or worse, as you're likely to get dragged through rocks and other shallowly buried obstacles.

Nearly every fall, avalanches catch eager riders and late-season hikers off-guard. Hunters traveling through the high country should exercise caution on steep, snow-covered terrain. Please consider the threat of avalanches if you visit steep slopes in the high country. Below we describe some considerations for early-season fall avalanche concerns.

We will update the Statewide Avalanche Conditions as necessary. On November 1, 2022, we will resume our daily weather forecasts. Our backcountry avalanche forecasts will begin in mid-November.

Weather Summary

Colorado received its first significant snowfall of the season between October 22 and October 27, bringing one to two feet of snow to the Elk Mountains. During this period the Upper Taylor SNOTEL Site, located about 4 miles to the east of the incident site, recorded 1.1 inches of snow water equivalent (SWE). The prior two days leading up to the incident the Taylor Park weather station, located 13 miles southeast of the incident site, recorded consistent light (1-16 mph) wind speeds with moderate (17-25 mph) gusts from the south and southwest.

Snowpack Summary

A series of storms in late September and early October brought small accumulations of snow to the high peaks of the Elk Mountains. On shady, north-facing couloirs and gullies above the treeline much of this early season snow developed into facets. Additional snow fell in the five days prior to the incident. Predominantly southerly winds drifted the additional snow onto north and northeast-facing slopes. Wind-drifted terrain features on Greg Mace Peak, including the couloir where the incident occurred, had a snowpack three to five feet deep.

Events Leading to the Avalanche

Skiers 1 and 2 planned to ski a north-facing couloir on Greg Mace Peak. They parked their car at the base of Pearl Pass Road and began hiking just before 7:00 A.M. on the morning of October 27. They ascended up a steep northwest-facing slope adjacent to the couloir. While ascending, Skier 1 noted “a firm crust below at the bottom of the snowpack below the new snow”.

The two skiers reached the ridgeline at 8:40 A.M. and began their descent at 8:50 A.M. Skier 1 descended first. He immediately saw “deep shooting cracks traveling maybe 10 feet in front of my skis.” Skier 1 continued into the couloir and stopped below a rock outcrop. He radioed to Skier 2 and suggested a ski cut at the top of the couloir to trigger an avalanche. Skier 2 skied diagonally across the top of the couloir and triggered a small slab avalanche within new snow (SS-ASc-R1-D1-S). Neither skier was caught in this avalanche.

Accident Summary

Skier 2 descended the bed surface of the intentionally-triggered avalanche. On his “second or third turn” Skier 2 triggered a larger avalanche that broke above him and into weak layers at the ground. The avalanche knocked Skier 2 off his feet and dragged down the slope. Skier 1 was able to watch his partner but lost sight of him towards the bottom of the couloir.

Rescue Summary

Skier 1 waited for the debris to come to a stop then switched his avalanche transceiver to search. Skier 2 called on the radio and said he was not buried. Skier 1 made a “very rocky and difficult ski down” to Skier 2.

The avalanche carried Skier 2 about 500 vertical feet to the bottom of the couloir. Skier 2 was thrown from the avalanche as it changed direction and flowed into a northwest-facing gully. The avalanche continued through the gully for another 700 vertical feet. Skier 2 lost both his skis and poles in the avalanche.

Skier 1, a certified EMT, took several minutes to ensure skier 2 had no serious injuries. Skier 2’s skis and poles were on top of the avalanche debris. They gathered the equipment and descended the rest of the slope.

Comments

This avalanche incident is a good example of the maxim “If there is enough snow to ride, there is enough snow to slide.” Although it was October and there was only one significant snowfall in the nascent season, Skier 2 triggered a large avalanche on a wind-loaded terrain feature and was dragged several hundred feet down a rocky couloir in a shallow snowpack. Luckily, he walked away with no serious injuries.

In hindsight skier 1 stated, “I should have stopped, turned around, and hiked out after I saw those shooting cracks.” Skiing, riding, or climbing in a couloir requires a level of exposure and commitment that most other terrain features lack. The best way to reduce your risk when committing to a consequential slope is to have a high level of confidence in the stability of the snowpack. Skier 1 skied an adjacent north-facing slope about 2000 feet to the west two days prior and saw no signs of unstable snow. This gave him some confidence that stability was better than it actually was on the slope they entered the day of the accident.

Slope cuts are typically performed by professional snow safety teams on controlled slopes within ski resorts or on small, inconsequential test slopes in the backcountry. They are meant to identify instabilities within recently deposited snow. Slope cuts are not intended to trigger layers of hard snow or persistent weak layers. The shooting cracks Skier 1 saw indicated a persistent weak layer, and not just storm-snow instabilities. As Skier 2 experienced, just because you trigger an avalanche in the upper portion of the snowpack, that does not mean the slope is then safe to travel on. Slope cuts are not a recommended technique for hard slab avalanches, on slopes above consequential terrain, or on slopes with a buried persistent weak layer.