Continuing snowfall and wind is out-pacing the snowpack's ability to adjust. Stay vigilant with simple terrain choices as this pattern continues.
In neighbouring Glacier National Park, a very large step-down avalanche may indicate that a deeply buried crust from late November is getting overloaded in some locations. Additional loading from new snow and wind continues to test deeper layers. Shallower but more sensitive storm slabs carry the risk of triggering one of these deeper weak layers.
Snowfall continues to accumulate and storm slabs remain reactive as slab depths increase and stiffen over a recently buried layer of surface hoar. Thicker slabs are found in wind-loaded terrain features, particularly near ridges. Conservative terrain selection is required to avoid this avalanche problem.
Saturday night: Cloudy, scattered flurries with 2-5 cm of accumulation, moderate to strong southwest wind, alpine temperature -8 C.
Sunday: Cloudy, 5-15 cm of snow, moderate to strong southwest wind, alpine high temperature -8 C.
Monday: Mostly cloudy with 5-10 cm of snow, light southwest wind, alpine high temperature -7 C.
Tuesday: Cloudy, 20-30 cm of snow, light southeast wind, alpine high temperature -5 C.
Widespread, large (size 2-3) natural and human-triggered storm slab avalanches were reported across the region on Saturday. These avalanches were 20-60 cm deep and were reported on all aspects and elevations. Some of these were remotely-triggered (i.e. from a distance).
A report of a larger (size 3.5) avalanche from nearby Glacier National Park indicates that the continual loading on more deeply buried weak layers remains a concern.
60-100 cm of new snow has fallen over the past week creating a touchy storm slab problem. At high elevations, this snow has been redistributed by strong southwest winds, loading lee features near ridges and exacerbating reactivity. The storm snow overlies a weak layer of feathery surface hoar and a hard melt-freeze crust on sun-exposed aspects, also increasing the reactivity of these slabs.
There are a couple more deeply buried weak layers, including a surface hoar layer from mid-December buried 110 to 180 cm deep and a facet/crust layer from late November buried over 180 cm deep. There is lingering concern that easier-to-trigger storm slab avalanches could step down to these deeper, persistent layers or that these weak layers could be human-triggered in areas in the alpine where the snowpack is thin, rocky, or variable.
