Sunday, February 5, 2023
Sunday, February 5, 2023
Ogden » Willard Peak
Location Name or Route
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Wind Drifted Snow
Started the tour today under cloudy skies that soon turned to heavy snowfall of approximately 1 inch per hour. Had a route planned to climb and to ski what we believed to be safe and protected from the recent winds. We had discussed the possible danger, and wind slabs were the top of the list to look out for. The planned climbing route is one I had used a few times in years past, but had most often used as a descent route. As I was climbing I noticed the wind cross loading slopes well above us, and we discussed the route that we planned to ski as it may have been in that zone. But we did not discuss the climbing route as we were not seeing much wind transport in that area.
The initial ascent route was in a tight creek bottom. Anything with some south aspect had rollerballed and had a stout crust from the day before. Just a few feet away north facing felt soft, with a slight density inversion 6-8" down. The skin track varied from crust stout enough to not break through, up to 8 inches of ski penetration. The light was very flat, and it was difficult to tell uphill from down in many places and slope steepness was hard to judge. This led to the mistake of being on this slope.
From looking at the map earlier in the tour, I had planned to be up out of the creek bottom and onto a north facing bench sooner, But with very few visual clues and the intense snowfall rate, I had missed this turn. As we were skinning up the drainage, I noticed the slope get steeper but struggled to plan the track due to the flat light. I could see some brush ahead and misestimated the slope angle between myself and the brush. As I climbed towards it, it became too steep to skin that direction so I stopped to kick turn to my right. As I completed my kick turn I heard a loud crack and the slope started to move.
As I had already changed direction my ski started to turn downhill and I was able to stay *mostly* on top of the debris. My partner, who was still facing uphill as the slide started, was sucked backwards, skis pulling under. I yelled for him to swim right as I was getting ready to go over the top of him. Luckily, the slope angle had gently backed off and the slide started to slow. When the snow stopped moving, I was able to take off skis and stand up. My partner was partially buried, waist deep with his head facing uphill, but downhill from his skis. His skis were under enough snow that I had to dig them out to release his bindings.
The maximum crown depth was three feet, and averaged around 18 inches. Crown was 45-50 feet wide and total slide distance from crown to toe was about 60 feet. The wind slab was very cohesive and stayed in large blocks through the avalanche. It entrained a shocking amount of snow for the size. The crown was on a slope angle of 35 degrees, and broke about 5 feet above us, right at a convex roll. The angle of the slope at the toe was 20 degrees.
We were very lucky that this happened on a slope with overall convexity with the slope angle backing off gently. Many places in the creek bottom we we're traveling through had sharp concave sections that could easily have been terrain traps. I am disappointed that I underestimated the amount of snow that had been loading in this zone over the previous days. Being fairly low elevation and in a tight drainage I mistakenly thought that the area hadn't seen much wind. I am also disappointed that I failed to recognize the windslab, and mistook it for a supportable crust. I don't think I had on my "avalanche eyes" at this point due to complacency and ease of travel. Had I been paying better attention to the route, and doing small checks of the snow along the way, I may have seen earlier signs of slab. One pole was lost, overall a very cheap lesson.