Avalanche Forecast

A fast-moving storm with intense snowfall and fierce wind moves in Friday afternoon.

Thursday night: Mainly cloudy, light southwest wind, alpine temperatures near -11 C, freezing level dropping to valley bottom.

Friday: Increasing cloud, 5-10 cm of snow starting in the afternoon as a potent storm moves in overnight, southwest winds increasing to strong by end of day, alpine temperatures rising to -6 C, freezing level rising to 600 m.

Saturday: Cloudy, 30-50 cm of snow expected to accumulate by late Saturday with heaviest precipitation overnight, strong southwest wind easing to moderate, alpine temperatures rising to -5 C overnight and dropping through the day to -11 C, freezing level rising to 1000m and dropping to 500 m.

Sunday: Cloudy, 10-20 cm of snow, moderate southwest wind, treeline temperatures near -7 C, freezing level around 500 m.  

On Wednesday and Thursday, there were multiple reports of small (size 1-1.5) human-triggered wind slabs on lee terrain features. This valuable MIN report detailing an avalanche involvement near Spearhead Peak on Wednesday provides an illustrative example of the wind slab problem in local terrain. 

On Tuesday, operators reported a large (size 2.5) cornice fall as a result of explosive work. 

The next storm arrives midday on Friday bringing 5-10 cm of snow and strong southwest wind. At upper elevations, a total of 15-25 cm of snow has accumulated in the past week over a substantial crust that formed in early December. A thin crust from a brief warm-up on Tuesday can be found within this snow. Strong west and southwest winds have redistributed available snow into dense wind slabs in wind-exposed areas. These wind slabs may be possible to human trigger in immediate lee terrain features (for example, just down-wind of ridges), particularly where the snow is poorly bonded to a crust.

We have uncertainty about the distribution of a layer of surface hoar or facets near the early December crust. Where weak snow exists near the crust, we anticipate a persistent slab problem to develop with rapid loading from the incoming storm. Send us your observations of what is above the crust where you are travelling using the Mountain Information Network.  

Average snow depths vary drastically with elevation, with 320-400+ cm in the alpine, 120-200 cm at treeline, and a drastic drop to below the threshold for avalanches below treeline. Deeper crust layers buried early season have transitioned to dormant.

• Be alert to conditions that change with elevation and wind exposure.
• Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
• Caution around slopes that are exposed to cornices overhead.