Buried weak layers within the snowpack continue to pose a threat to backcountry travelers. The likelihood of triggering large avalanches involving these layers has decreased which makes it difficult to predict what slopes may fail. Tracks are not an indication of stability as failure may occur only when a thin, weak spot in the slope is impacted. Avoid steep terrain where cliff bands or rocks may provide areas of shallow coverage. Recent snow can also be released as shallow wind slabs at the high elevations.
Although becoming less likely, a chance continues for a single person to trigger large, hard slab avalanches. These slabs could have depths of two to five feet at the upper elevations and have depths to three feet at the mid elevations. Keep in mind that these slabs could break high on a slope when a weak point is impacted mid-slope. Avalanches are unlikely at the low elevations today.
Shallow wind slabs with depth of 4-10 inches lie in steep avalanche terrain at the upper elevations. These soft slabs were formed by west winds. Backcountry enthusiast should look for signs of wind loading and watch out for areas where even a small slide could carry someone over a cliff edge or into a terrain trap.
Weak layers lie within the snowpack. The most prominent layer was formed during the dry period in November, however more recent weak layers can also be identified. In the Tetons, these weak layers have become less prone to failure, however there remains a chance for releasing one if a weak spot on a slope is impacted. It is a very tricky time as determining specifically which slope may still fail is difficult. Getting out a shovel and looking at the snowpack can help to identify the presence of the layers but stability test can be misleading as the weaker areas may exist further down or out on a slope.
The mid-week storm that had very strong winds provided for a period of instability in the upper portion of the snowpack. Slab avalanches involving this recent snow have become unlikely except in extreme terrain as the snowpack has now adjusted to it. Yesterday the snow from the previous 24 hours was active above 8500’ where wind and increasing temperatures resulted in very sensitive soft slabs with depths of 4-8 inches in very steep terrain. These slabs will be less sensitive today but could still be triggered as new snowfall accumulates and temperatures continue to rise.
The crew at B-TAC wishes all a Happy and Safe Christmas Day and Holiday Season.
