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Avalanche Forecast

Archived

Dec 5th, 2019–Dec 6th, 2019

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Rockies.

Caution as you transition into wind-exposed terrain. Avalanches are possible where wind slabs have formed in the alpine.

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

Thursday night: Cloudy, isolated flurries with a trace of accumulation, moderate southwest winds, alpine temperature -3 C, freezing level around 1000 m.

Friday: Mix of sun and cloud, isolated flurries with a trace of accumulation, moderate southwest winds, alpine high temperature near 0 C, freezing level around 1700 m.

Saturday: Cloudy with periods of sun and snow with 2-5 cm possible, moderate southwest winds, alpine high temperature -2 C, freezing level dropping from around 1500 m

Sunday: Decreasing cloud cover, 5-15 cm of snow, light northerly winds, alpine high temperature -8 C

Avalanche Summary

There have been few recent avalanches reported in the region. A couple of small wind slabs triggered by explosives have been observed. 

Large explosives in early season control work triggered several large avalanches stepping down to deeper weak layers. While human triggering these larger avalanches remains unlikely in the short term, these results are indicative of a persistent weak layer lingering in the snowpack that may become reactive with additional loading. 

Snowpack Summary

Ongoing strong westerly winds have likely been creating wind slabs at upper elevations on lee terrain features. Snowpack depths are highly variable this early in the season with amounts ranging between 50-100 cm at higher elevations, and tapering rapidly below treeline (check out this MIN report from Imperial Ridge). A crust has been reported in the middle of the snowpack.

If you are getting out into the mountains, let us know what you see by posting to the Mountain Information Network!

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.