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Avalanche Forecast

Archived

Dec 8th, 2021–Dec 9th, 2021

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

Regions

Vancouver Island.

Pay attention to how the wind has drifted snow as you gain elevation. Areas with drifted snow over a crust may be reactive to human triggering, especially near ridges and roll-overs. 

Confidence

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

Weather Forecast

Wednesday night: Mainly cloudy, isolated convective flurries with trace accumulations, moderate west wind, temperatures dropping to -5 C, freezing level dropping to 600 m.

Thursday: A mix of sun and cloud, moderate northwest wind, temperature rising to -4 C near treeline, freezing level rising to 700 m.

Friday: Cloudy, 5-15 cm of snow with a storm moving late afternoon, wind becoming southwest and increasing to strong, temperatures rising to near freezing at treeline by end of day, freezing level rising to 1000 m.

Saturday: Cloudy, 10-25 cm of snow expected to accumulate overnight and into the morning, strong southwest wind, freezing level rising to 1300 m overnight during heaviest precipitation and dropping to 500 m by end of day. 

Avalanche Summary

No recent avalanche activity has been reported. 

Snowpack Summary

At upper elevations, 20-40 cm of snow has accumulated in the past week over a substantial crust that formed during the last big rain event. A thin crust from a brief warm-up on Tuesday can be found within this snow. Moderate winds have likely redistributed available snow into wind slabs in wind-exposed areas. These wind slabs may be reactive to human triggering in immediate lee terrain features (for example, just down-wind of ridges), particularly where the snow is not well-bonded to crust layers.

We have a lot of uncertainty about the composition and reactivity of the widespread rain crust interface. We suspect there may be surface hoar or facets above the crust. As snow gradually accumulates and settles into a cohesive layer above it, we are vigilantly tracking this layer ahead of the incoming weekend storm. Send us your observations of what is above the crust where you are travelling using the Mountain Information Network. 

Recent indications of the region's snowpack suggest that snow depths in the alpine are 150- 200 cm. At treeline, snow depths taper dramatically to 40-80 cm. Below treeline is below the threshold for avalanches.

Terrain and Travel

  • Be alert to conditions that change with elevation and wind exposure.
  • Wind slabs may be poorly bonded to the underlying crust.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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.