Tuesday, November 23, 2010

Decisions

Daren and I went backcountry skiing Saturday morning. Winds were nuking—at one point I had to hunch over to avoid being blown over.

Wind is not conducive to avalanche safety. Wind can redistribute snow into wind slabs many times thicker than a layer of new snow from even the largest storms. So we made the decision not to ski the north-facing slope on the lee side of the ridge we had just climbed. The south-facing aspect was surprisingly good.

Sunday morning, Daren sent me a text asking if I had seen Bart’s observation from Saturday. Same aspect and elevation, less than 200 meters from the slope we were considering skiing.

As you can see from the picture of the Samurai holding his pole up, that wind slab was pretty deep.

This morning, Mike H., Tanner, and I were back to the same spot. The wind was still blowing.

Dug et al opted not to even poke around Days and skied the south aspect out. But we figured we were there, so we may as well check the snow out.

Mike kicked half a dozen cornices and didn’t get anything to move. He kicked one particularly large cornice directly above the lower angle slope we were considering skiing, and nothing moved. “That cornice was definitely heavier than a skier,” he observed.

Still, we decided to dig a pit. We did an extended column test that failed and propagated about 60cm deep with a Q1 shear at four taps with just the weight of my hand. Below the slab that failed was a layer of sugary, faceted, weak snow.

Anything that fails with the weight of your hand is a red flag. Anything that shears at Q1 (a clean break between two layers) is a red flag. Put the two together, and it may not matter that the slope is less than 30 degrees.

The south aspect skied great. Snow was soft, and even though visibility was poor, it was still fun. Incredibly fun when you consider it’s still November. Tanner headed to Alta for more first tracks. Mike and I went to work. When I got to work, I read the following in today’s avalanche forecast:

Dropping a cornice on a slope, seeing no results, and diving in is asking for trouble.

Um, yeah.

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