Sunday, January 09, 2011

A Weatherwax avalanche

The clouds and frost made the skiing scenery magical
Skiing through the avalanche debris, which did much damage

Large blocks of snow could have killed anyone in their path

Skiing our way out from Weatherwax bottom
 Our ski to the Weatherwax bowls in the Little Belts Saturday was more educational than recreational.
The area is found by going up the road behind the Forest Service cabin at Kings Hill Pass.  Cross country skiers know this as the Deadman trail. The bowls lie just north of the powerlines at the top of the hill, some 2 miles away.
The snow-covered trees and moisture-laden black clouds on the horizon made this trip an aesthetic pleasure. The trees were flocked in a snow-ice mixture.
We were headed for lower angle open slopes east of the large open areas frequented by snowmobilers. The area we were headed into is more an opening in the trees than a bowl, but large enough to pull multiple telemark turns.
Just beyond the powerlines we got on the ridge above the large open snowmobile bowls and began looking for the opening.
Before we got there, though, we think we broke off a wind-loaded cornice that triggered a fairly sizeable slab avalanche over an area about the width of a football field that tumbled in waves down into the trees some 300-500 feet below.
I watched in a sort of surprised disbelief.
I had witnessed several small avalanches in the Little Belts over the past 30 years of backcountry skiing, but nothing like this. One time in the south Deadman bowls we triggered an avalanche beneath us where a couple hundred feet of slab slid.  In the Ranch Creek bowls we had seen isolated, small slides.
Later, we found our way into the Weatherwax slide area for a look.
What we found was a lot of snow, rock and tree debris that looked like a field of dirty cottage cheese. Some trees had held back the snow and large blocks of the sheered snow slabs. Those slabs were strewn along the treeline below us.
I measured the slope angle in the area and found it at roughly 45 percent grade.  The ideal avalanche angle is above 30 percent.
The avalanche had gone down to the ground.
We dug a snow pit on the adjacent slope and I figure there was some three and a half and four feet of snow on these slopes.  About 18 inches of new snow sat atop a layer of hoar frost, which didn’t seem to be much of factor because everything beneath it was also swept away.
We did the shovel compression test on a snow column in the pit and the snow there was quite stable.  I couldn’t get my column to collapse.
So, we spent a couple of hours doing turns in deep and sometimes soft pockets of snow that made the skiing halting at time.
We then very slowly and painstakingly worked our way back to the ridgeline where a wind and snow storm had moved in.
The unstable slopes didn’t seem to faze the snowmobilers who played the afternoon away on Weatherwax, without any apparent avalanche consequence.
I found this avalanche experience quite sobering, however.  We’ve skied much steeper and slab areas in the Little Belts in the past without this consequence.
I had never seen a slide like this in this mountain range.

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