Avalanche Forecast

Monday night: Decreasing cloud, 2-5 cm of snow, light southwest winds, alpine temperature -3 C, freezing level dropping to 200 m.

Tuesday: Increasing cloud, 2-5 cm of snow, moderate south wind increasing to extreme overnight, alpine high temperature -2 C, freezing level rising to 500 m.

Wednesday: Mostly cloudy, 35-50 cm of snow, strong southwest winds with extreme gusts, alpine high temperature -1 C, freezing level rising to 800 m.

Thursday: Mostly cloudy, 30-40 cm of snow, strong south winds with extreme gusts, alpine high temperature -1 C, freezing level around 800 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.

Ongoing snowfall and wind continue to build reactive slabs in lee and cross-loaded terrain features. Around 50-120 cm of storm snow over the past week is settling rapidly. The storm snow rests on a mix of extensively wind affected surfaces at upper elevations 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. With more snow in the forecast later in the week, the reactivity of this layer will be important to track. Below tree line, a recent warm-up moistened snow surfaces up to 900 m, forming a temperature crust. This MIN report provides a helpful description of these conditions near Terrace. 

A crust from mid November lurks at the base of the snowpack. The last reported avalanche on this layer was Jan 17th, and it will most likely require a large trigger such as explosives or cornice fall to initiate this deep persistent slab problem.

• Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
• Expect slab conditions to change drastically as you move into wind exposed terrain.
• Stay off recently wind loaded slopes until they have had a chance to stabilize.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.