Avalanche Forecast

Issued: Jan 15th, 2021 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Deep Persistent Slabs.

Avalanche Canada ahanna, Avalanche Canada

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Be mindful of buried weak layers. Recent persistent slab avalanches have been large, destructive and difficult to predict. This is not the time to be pushing into aggressive or committing lines. Uncertainty is best managed through conservative terrain selection. 

Summary

Confidence

High -

Weather Forecast

Friday night: Partly cloudy, light to moderate northwest wind, freezing level 700 m.

Saturday: Mix of sun and cloud, light southwest wind, freezing level 1100 m.

Sunday: Snow overnight, 5-15 cm, moderate southwest wind, freezing level 1100 m.

Monday: Mix of sun and cloud, light to moderate northerly wind, freezing level 1300 m with an above freezing layer developing.

Avalanche Summary

Explosive control work targeting cornices on Friday produced results up to size 2. On Wednesday, there were reports of a natural storm slab avalanche cycle up to size 3. There were also several that stepped down to deeper weak layers resulting in very large (size 3-4) persistent slab avalanches. Check out this MIN describing a large cornice-triggered avalanche in the Blackcomb sidecountry on Thursday.

Last Saturday, a large (size 3) avalanche was remotely triggered by skiers on Cowboy Ridge near Whistler. The avalanche occurred on a north to northwest aspect at around 1900 m. The crown ranged reached up to 200 cm and was approximately 200 m wide. Check out this MIN for photos and more information. A similar avalanche was remotely triggered by skiers on a nearby westerly slope a few days before; check out this MIN for more info and photos.

Snowpack Summary

Variable wind effect in the alpine includes scoured windward aspects, sastrugi, hard slab, wind pressed surfaces over lower density snow and isolated pockets of soft snow in sheltered areas above 2000 m. Wind slabs may remain sensitive where they overlie surface hoar in sheltered terrain or a crust on solar aspects. A widespread surface crust exists below 1900 m.

The snowpack is currently quite complex. Layers of surface hoar as well as sugary faceted grains above a hard melt-freeze crust from early December may be found down 100 to 200 cm. Last weekend, several large natural and human-triggered avalanches on this layer occurred, with the hot spots being around the Whistler backcountry.

Near the base of the snowpack, there may be faceted grains above a crust from early-November, which was identified as the failure layer in recent sporadic avalanche releases. At this depth, avalanches are large and destructive.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Cornice failure may trigger large avalanches.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
  • In times of uncertainty conservative terrain choices are our best defense.

Problems

Wind Slabs

An icon showing Wind Slabs

Previous wind has deposited recent snow into deeper slabs on leeward slopes at upper elevations. Wind slabs may remain reactive, particularly where they sit over surface hoar in sheltered terrain or a crust on solar aspects. Cornices have grown large, saggy and fragile.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

A couple of problematic layers may be found around 100 to 200 cm deep, including weak layers of surface hoar and faceted grains above a hard melt-freeze crust. A few high-consequence avalanches have been triggered naturally and by riders recently near Whistler.

Read what a local guide has to say about these persistent weak layers here.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Jan 16th, 2021 4:00PM