Avalanche Forecast
Issued: Dec 15th, 2021 1:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
JSmith,
Avalanche Canada
The current persistent slab problem is best managed through conservative terrain choices and disciplined backcountry travel techniques.
Avoid likely trigger spots such as steep, rocky terrain, with a shallow or thin to thick snowpack.
Summary
Confidence
Weather Forecast
WEDNESDAY NIGHT: Cloudy / Light, southwesterly winds / Low of -8 C / Freezing level 200 m.
THURSDAY: Mix of sun and cloud / Light, northwesterly winds / High of -5 C / Freezing level 400 m.
FRIDAY: Increasing cloudiness / Light, northwesterly winds / High of -7 C / Freezing level 300 m.
SATURDAY: Snow; 30-40 cm / Extreme, southwesterly winds / High of -2 C / Freezing level 800 m.
Avalanche Summary
A couple naturally triggered size 2 storm slabs were reported in the alpine on Tuesday.
Several human triggered persistent slab avalanches up to size 2, failing on the early December crust were reported on Monday. See one example in this MIN report.
Snowpack Summary
Recent snow and strong southerly winds formed wind slabs on lee features in open terrain that may remain reactive to human triggers.
The primary layer of concern in the snowpack is a crust down 100-180 cm that was formed in early December. This layer has a weak layer of small facets (sugary snow) above it that has been the cause of recent large avalanches.
This has created a Persistent slab problem that is tricky to manage and likely to surprise riders who choose to ride steep, rocky slopes with a shallow or thin to thick snowpack.
It's tricky to manage because it's unlikely to trigger this layer on many slopes, but the consequence of triggering it is massive.
This scenario requires conservative terrain choices and disciplined backcountry travel techniques.
Terrain and Travel
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Cornice failures could trigger very large and destructive avalanches.
- Uncertainty is best managed through conservative terrain choices at this time.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
Problems
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 100-180 cm near a crust layer that formed in early December. The persistent slab problem has demonstrated recent instability, and it may be possible to human trigger. Avoid likely trigger spots such as steep, rocky slopes with a shallow or thin to thick snowpack.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Lingering winds slabs may remain reactive to human triggers. Avoid slopes where the snow feels stiff or "slaby" and seek out better riding in wind sheltered terrain.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 16th, 2021 1:00PM
