Snow Sports Weather - Module B: case ID = s11

This module was not based on an avalanche accident because, despite the new snow, avalanche conditions were mostly safe. The pre-existing snowpack was well-consolidated and bonded. The new snow came in right-side-up since it was associated with a cold front. As eluded to in the snow observations and the avalanche forecast, sluffing would have only presented an issue in very steep terrain. Further, the generally light winds with this storm would have created small, relatively soft, wind slabs in the most wind-exposed locations. If you chose to do the backcountry trip, it's very unlikely you would have had an avalanche accident (at least not one resulting in injury or death) on your proposed route.

However, even small wind slabs can be dangerous if encountered in the wrong place. An example of this was an accident in the Cayoosh area off the Duffy Lakes Road (northeast of Pemberton). A group was headed to ski the "Million Dollar Couloir". The couloir is approached from a wind-exposed ridgeline above. It requires traversing a narrow section of ridgeline with a slope angle of about 40° (very steep). It's east-facing, with a sharp drop-off and a large cornice (overhanging snow) to the west, and becomes increasingly steep to the east, eventually rolling off over a cliff below.

The group was concerned about getting too close to the cornices to the west (which could break off unexpectedly), so they traversed closer to the cliff-exposed side. The first skier traversed without incident. The second skier traversed part way and stopped to wait for the third. The third skier stopped just below the second, with just enough space between for the third to put his pack down. His pack was off and he was facing uphill when the wind slab they were on fractured between the second and third skier. The third skier tried to dig his edges into the slab and bed of the avalanche to stop, but a chunk of snow from above knocked him off balance. He was carried downslope 15-20 m where he went off the cliff.

He fell 125 m and was subsequently buried by avalanche debris. The cliff band made it difficult to route-find and get down to the victim. By the time the first person got to avalanche debris, 15-20 minutes had elapsed. They located him immediately, but it was too late. The victim's face was blue and he did not respond to CPR.

The weather in your scenario evolved as expected. 15-20 cm of fresh snow fell overnight. Snow showers and flurries tapered during your ski day Saturday, becoming mostly sunny with a few cloud bands (see IR Satellite Loop below). Winds were light from the northwest. This would have provided good weather for a backcountry day, and excellent snow surface conditions for skiing.

Related Stories and Links

• I was once caught in a bad spot due to wind slab avalanche danger. We were on the northwest face of Castle Towers Mountain near Garibaldi Lake. The snowpack was generally very stable. We had just skied a 55° face with just a bit of sluffing.

  

  (Credit: West)

  Lower down, on a more mellow section, we could tell there had been a bit of wind-effect, creating a thin, somewhat-stiff wind slab. As I was skiing across a mellow, convex slope, the wind slab shattered around me, propagating. There were no consequences, as the slab was very shallow, and the run out didn't pose any danger. I was able to simply ski out of it.

  

  (Credit: West)

  However, lower down on the face we had to cross a very similar slope. Except this time it was larger, and the run out funnelled down into a crevasse. We were trapped; this slope was our only way off the northwest face. I took a known, calculated risk, and took a fast, descending traverse across the slope, keeping as much speed as possible so that if I triggered a shallow wind slab I could ski out of it. The slope fractured, but even higher above me than expected. There was enough mass this time that it knocked me off my feet. I did a forward somersault, somewhat miraculously ending up back on my feet with both skis, and continued to ski down, across, and out of the slide.

  

  (Credit: West)

  In the above photo you can just barely make out the crown (or fracture line) of the avalanche, in the upper right near the rocks. You can also see the ugly crevasse I would've been carried down into. That was a very bad scenario to be in.

  If I was less lucky, or not as strong of a skier, it could've ended up very differently for me. A safer option might have been to put skins on, and climb back out the way we came. In that case we may have encountered other hazards like running out of daylight. You can do your best to minimize risk, but you can't completely eliminate it. As with the Million Dollar Couloir accident above, any time you step up the seriousness of the terrain you're in, you're also stepping up the consequences of any mistakes.

• Here is part two of the compelling 4-part series on avalanches and decision making. We are posting one part per module.
  Part Two: Human Factor: Chapter 2

If you could start over for this particular case study (knowing the actual outcome from Step 7), what would you do differently?

For example, would you make a different decision?

Would you want more or different data to help you make your decision (if so, which data), etc.

Enter your statements into the UBC Canvas system, for the module: Snow Sports s11 Step 10.

These count towards your grade (for grade weights, see the Evaluation link from the course home page). The grade is based on the relevance of your statements for the scenario of this learning module, and on the indication that you learned from your mistakes (if any), not on the amount of statements you make. Please be brief/succinct.