Avalanche Forecast

Wednesday night: Lingering flurries bringing a final 5-10 cm of new snow. Light to moderate southwest winds.

Thursday: Cloudy with isolated flurries and a trace of new snow. Light to moderate southwest winds, shifting northwest by evening. Treeline high temperatures around -1 with freezing levels reaching 1500 metres. 

Friday: Mainly sunny. Light northwest winds shifting southwest. Treeline high temperatures around -1, alpine reaching 0, cooler at lower elevations under a temperature inversion.

Saturday: Cloudy with scattered flurries bringing up to 5 cm of new snow. Light to moderate southwest winds. Treeline high temperatures around -3 with freezing levels to 1100 metres.

A wide range of different avalanche activity was noted on Tuesday, with at least one operator in the region reporting numerous releases up to size 2 (large). A natural size 3 (very large) wind slab avalanche also crossed the Trans-Canada highway in Glacier National Park. Expect sporadic very large avalanches of this kind to occur for the next couple of days. 

The persistent early December crust/facet layer has recently been active in this region. Concern for persistent slab activity like this is being sustained by new snow, wind, and warming.

On Monday, a few very large simultaneous remote triggered persistent slab avalanches were reported in this Mountain Information Network (MIN) report south of Kaslo. It reported as a near miss, triggered from 150 m away on northeast through southeast features around treeline. The crown was one meter deep and propagated 500 m wide.

On Friday, three naturally triggered size 2-3 avalanches on this layer were reported in mountain ranges just west of the Columbia river. They were reported at treeline and above on south and east aspects. Some were known to be windslab avalanches that stepped down to this deeper, persistent layer in a thin, rocky area. 

Continuing snowfall is expected to bring new snow totals to 20-40 cm by Thursday morning. Melt-freeze or rime crust may be found partway within the new snow in some areas, introducing a new likely failure plane and limiting wind transport where it exists. The new snow has formed a storm slab problem above a mix of settling storm snow and windslabs in the upper snowpack after several days of consistent snowfall and southwest wind.

Our new snow and another 50-90 cm of recent storm snow will be settling on top of weak, faceted snow that formed during the recent cold snap. As new snow accumulates and temperatures rise, the upper meter of the snowpack may become increasingly upside-down and more likely to avalanche. 

We're actively monitoring the early December crust. In some places, it's down 80 cm, while in wind-loaded terrain features it can be found as deep as 180 cm below the surface. It consists of faceted grains above a bulletproof crust formed by the Atmospheric Rivers of early December. There has been avalanche activity on this crust over the weekend. Larger avalanches in surface layers as well as natural cornice falls may have potential to step down to this layer in the coming days.

• Choose conservative terrain and watch for clues of instability.
• The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.
• Avoid areas with overhead hazard.