Avalanche Forecast
Issued: Jan 16th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs, Wind Slabs and Cornices.
ahanna,
Avalanche Canada
A lick of new snow may slide easily on the crust. A high degree of uncertainty around deep layers in a complex snowpack is best managed through conservative terrain selection. This is not the best time to dive into ultra committing lines.
Summary
Confidence
Weather Forecast
Saturday night: Snow, 5-10 cm, light to moderate southwest ridgetop wind, freezing level 800 m.
Sunday: Mostly cloudy, light to moderate southwest ridgetop wind, freezing level 1100 m.
Monday: Sunny, light to moderate northerly wind, freezing level 1300 m with an above freezing layer developing around 2500 m.
Tuesday: Sunny, moderate southwest ridgetop wind, freezing level 1000 m, above freezing layer breaking down.
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. A layer of 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
Deep Persistent Slabs
A couple of problematic layers may be found around 100 to 200 cm deep, including a weak layer of faceted grains above a 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
Expected Size
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.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Cornices
Cornices have grown large, saggy and fragile. A few recent cornice falls have triggered avalanches on the slopes below. Many that haven't fallen are showing pull-away cracks.
Aspects: North, North East, East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Jan 17th, 2021 4:00PM
