Avalanche Forecast
Issued: Dec 25th, 2023 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 Persistent Slabs.
zryan,
Avalanche Canada
Weak layers in the mid and lower snowpack have produced large natural and human-triggered avalanches in recent days.
Manage this problem with conservative terrain choices.
Summary
Confidence
Avalanche Summary
A natural avalanche cycle occurred on Friday night. Several large (size 2 to 3) storm slab, persistent slab, and deep persistent slabs were reported from the alpine and treeline.
Over the weekend, many large (size 2 to 3) natural and rider triggered (some remotely triggered) persistent and deep persistent slabs were reported in the alpine and treeline.
Moving forward, natural avalanche activity is expected to taper, but large human-triggered slabs remain possible.
Snowpack Summary
Recent storm snow has been redistributed into wind slab near ridge crests by strong winds. Below treeline a new crust is on or near the surface.
The mid pack contains several layers of note; a layer of surface hoar and a crust down 20 to 40 cm, a significant crust from the early December rain event down around 50 cm and a layer of surface hoar down 50 to 90 cm.
The make up of the lower snowpack is variable throughout the region, in shallower snowpack areas, basal facets exist. This is most concerning in shallow alpine areas.
Weather Summary
Monday Night
Increasing cloud cover with isolated flurries. Alpine wind southwest 30 to 60 km/h. Treeline temperature -4 °C.
Tuesday
Cloudy with snowfall, up to 5 cm of accumulation. Alpine wind southwest 30 to 60 km/h. Treeline temperature -4 °C. Freezing level rising to 800 m.
Wednesday
A mix of sun and cloud with isolated flurries. Alpine wind southeast 30 to 70 km/h. Treeline temperature -4 °C.
Thursday
Cloudy with snowfall, up to 5 cm of accumulation. Alpine wind south 30 to 60 km/h. Treeline temperature -3 °C. Freezing level rising to 1000 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Keep in mind that human triggering potential persists as natural avalanching tapers off.
- Use careful route-finding and stick to moderate slope angles with low consequences.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Use ridges or ribs to avoid areas of wind loaded snow.
Problems
Deep Persistent Slabs
A weak layer of basal facets has produced large natural and human-triggered avalanches in recent days. This problem is most likely to be an issue in shallow snowpack areas in the alpine.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Wind slabs have formed on lee features in exposed terrain at treeline and above.
If triggered, wind slabs have the potential to step down to deeper layers, creating a larger that expected avalanche.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer of surface hoar is down 50 to 90 cm and is still concerning where a significant crust is not found above it.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 26th, 2023 4:00PM
