New Year, new snow

Wednesday, January 06, 2010

By Lisa Van Sciver

Jackson Hole, Wyo.-Twenty-ten rolled in with a weeklong storm dropping more than two feet of snow in the mountains. The skiing possibilities increased, along with the avalanche hazard. New snow loaded slopes and added stress to weak, base layers, consisting of large, grain depth hoar. The new snow, transported by the wind, has created up to a three-foot slab, which has been sliding on old snow surfaces. When triggered, the new slab has stepped down, releasing old, buried slabs to the ground.

Last Saturday, after the storm’s heaviest snowfall, avalanches appeared on all aspects between 8,000 and 9,500 feet. Many of these avalanches were remotely triggered by surprised skiers. In areas without old ski tracks there is still significant collapsing. On Taylor Mountain’s east face there is visible avalanche activity, where two slabs pulled out to the ground and ran 200 feet.

In Cooke City, they are experiencing a similar weak snowpack structure, and on Sunday a snowmobiler was caught and buried in the LuLu Pass area, Montana’s second avalanche fatality this season.

Digging pits and stability tests are a great way to become familiar with the snowpack, but when using these tests, spatial variability needs to be considered. In one pit, stability test have proven the snowpack to be fairly stable and incredibly weak. This weak and variable snowpack seems to be releasing with the right trigger, which could be an added load, temperature change, or shallow pocket. Currently, experienced route finding is essential in the backcountry.   



PERMALINK:
New Year, new snow | Planet JH News Article: Snow Report Column

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