Avalanche Forecast

Tuesday night: Cloudy, 15-25 cm of snow above 800 m, extreme south wind, alpine temperature -1 C, freezing level rising to 1000 m.

Wednesday: Cloudy, 10-20 cm of snow above 800 m, strong southwest winds, alpine high temperature -2 C, freezing level around 800 m.

Thursday: Mostly cloudy, 35-45 cm of snow above 800 m, strong south winds with extreme gusts, alpine high temperature -1 C, freezing level around 800 m. 

Friday: Cloudy, 25-35 cm of snow above 500 m, strong south winds, alpine high temperature -2 C, freezing level around 600 m.

Small pockets of human-triggered wind slab were recently reported at treeline elevations closer to Terrace, while larger (size 2-3.5) wind slabs were reported further north in the Bear Pass area releasing naturally from alpine start zones. Several of these avalanches released down to a weak layer formed in mid-January. During the weekend warm-up, numerous natural loose wet avalanches in steep terrain (size 1-2) were observed up to 1000 m. 

Reports of deep persistent slab avalanches have been trickling in throughout the month, with the last reported event occurring on Jan 17th. They are associated with a November crust layer near the base of the snowpack which has produced very large avalanches (size 3+) with crown depths of around 2 m. These have typically run in alpine terrain, on lee or cross-loaded slopes. Recent loading has been a good test for this layer and it seems to be trending less reactive.

A powerful storm is impacting the region with intense snowfall, extreme winds, and fluctuating temperatures. Rapid snow accumulations are expected to build a touchy storm slab problem, particularly in wind-exposed areas. The intensity of the wind has the potential to reach areas well below treeline and form slabs in normally sheltered areas. Fluctuating freezing levels throughout the storm present an additional layer of complexity that may promote instability in the storm snow.

Last week's 50-120 cm of snow accumulation rests on a mix of previously scoured surfaces from the arctic outflow winds or a thick layer of weak facets. Recent avalanche activity in the Bear Pass area and snowpack tests results have indicated that this layer is still a concern (check out this MIN report). Below tree line, a recent warm-up moistened snow surfaces up to 900 m, forming a temperature crust. 

A crust from mid November lurks at the base of the snowpack. The last reported avalanche on this layer was Jan 17th. While it is promising that last week's significant snowfall did not trigger avalanches on this deep persistent weak layer, there is lingering uncertainty as to whether this week's weather could meet the threshold. 

• Watch for changing conditions today, storm slabs may become increasingly reactive.
• Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
• Be aware of the potential for human triggerable storm slabs at lower elevations, even on small features.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.