Local Avalanche Incidents

February 25th, 2012 - Five Mile Creek, Chilkat Pass

Location:Near the top of "Girlfriend Hill", 5-mile creek, Chilkat Pass, BC, Canada: 59.508757N, 136.443726W
Date/Time of Occurrence: 2/25/12, ~2:00pm
Mode of Travel: Tele skis (Skier 1), A/T skis (Skier 2)
Accident Type: Partial burial
Number in Party: 2
Persons Buried: 1
Persons Injured: 0
Persons Killed: 0
Avalanche Details:
Type: SS - Soft slab avalanche
Trigger: AS - Skier Triggered
Size: D1, R3
Sliding Surface: I - New/Old snow interface
Aspect: SW
Elevation: ~700m
Slope Angle: ~40
Depth: 30-40cm

Weather and Snowpack Summary:
After ~8cm of weak snow on the 18th, an upside-down storm brought 25-40cm of snow (at a 14:1 ratio) to mountain areas on the 20th. Cloudy and cool conditions early that week yielded to clear skies, sunshine, cold nights and below-freezing days. Winds were light to moderate through the week.

The 25th was another outstanding day. Sunny and cool with light NW winds. High temperatures were 28 and 30 degrees F in Haines (at sea level), and Customs (~250m MSL) respectively, suggesting a temperature inversion through the day.

The report posted by the Haines Avalanche Information Center for the day stated moderate danger in this zone, with the details:
"An observation from above treeline Wednesday showed little strengthening of Monday's unstable storm snow. While this "upside-down" storm snow has had several days to sit, the cool temperatures and lack of compressive weight are preventing the kind of quick strengthening we've been used to this winter. This lingering danger needs to be carefully assessed on all steep slopes this weekend, especially wind loaded north aspects. Pockets of CONSIDERABLE danger likely lurk in these areas."

Skier 2 performed an Extended Column Test near the crown, and found that the 30cm upper block fractured across the column after 4 taps from the wrist, then slid off after 7 taps.

Details of the Incident:

Two American skiers skinned up from the Highway near 5-mile creek (on the Canadian side of the border) on a sunny, calm day. Both were wearing beacons. They performed a beacon check at the trailhead and noted that the batteries were low on one of the beacons. Neither skier had checked the Haines Avalanche Information Center's report for the area that day, but they had talked to friends who dug a snowpit the previous weekend on a slope in the area.

They skinned up to the crest of a hill about 300m above the road, and skied 4 laps in the gladed treeline zone on the SW aspect towards the road. Skier 1 noted throughout the day that he figured the top 30cm of snow could slide, but the terrain they were on would make such a slide of low consequence. The skiers probed with their poles on the uphill, noting a weakness below the top 30cm or so of powder snow. Skier 1 was not overly concerned, considering that the area is very popular and often thought of by locals as a "safe" place to ski.

With each successive run they veered slightly to the south of their previous tracks. Thus, by the fourth run, they were on slightly different slopes than they had skied before. It was on this fourth run that Skier 1 triggered the avalanche.

Skier 2 skied down around a short, steep, wind loaded slope with pillows or cornices at the top, avoiding the steepest part of the slope. He stopped behind some trees in a safe zone about 30m below the slope to wait for his partner.

As Skier 1 followed, he noticed good snow on the steep, wind loaded slope and veered out onto the center of the slope. Skier 1 fell in the center of the steep slope, and a slab avalanche broke around him. Already down in the snow, he was carried by the debris which was moving in large blocks about 30cm thick. His skis were caught by the debris and he was pulled under one of the large blocks. By the time the skier and debris came to rest at the bottom of the slope about 20m lower, Skier 1 was on his back with his head downhill and blocks of snow atop him up to his chest. The slab slid on a loose and weak layer at the new/old snow interface.

Skier 1 couldn't move at first, but was able to extract himself after struggling for a short bit. By the time Skier 2 had climbed up to help, Skier 1 had dug himself out without injuries.

Both skiers were surprised at the potential danger that such a small slope can pose. Skier 1 remarked, "If there was more new snow, the slope could have been pretty dangerous."

Analysis:

These skiers were sticking to low-consequence terrain throughout the day, and were having a great time at it. By the fourth run they were feeling confident about where they were, despite the concern in the back of their minds about the top 30cm of snow. By the last run of the day, it was easy to venture onto that short steep pitch on the way down.

This kind of decision is made often by skiers who otherwise do everything right and manage risk conservatively. They are sometimes surprised by the results!

This is a good example of how the small, unsuspecting slopes in the middle of our uphills and downhills can sometimes present the biggest dangers of the day. Had this been a deep powder day after a big storm, a full burial could easily have occurred on this slope.

Watch out for those small slopes! Far too many groups overlook these dangers and needlessly expose themselves to similar slopes without much thought, especially on the uphill.