Avalanche Forecast
Issued: Dec 26th, 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 last Friday. 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 has tapered, but large human-triggered slabs remain possible.
Snowpack Summary
Recent strong winds have created heavily wind-affected surfaces in the alpine and treeline. 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
Tuesday Night
Clearing. Southwest alpine wind 50 km/h dropping to 20 km/h. Treeline temperature -5 °C. Freezing level dropping to valley bottom.
Wednesday
A mix of sun and cloud. South alpine wind 20 to 40 km/h. Treeline temperature -3 °C. Freezing level rising to 500 to 1000 m.
Thursday
Cloudy with snowfall, 1 to 5 cm of accumulation. Southwest alpine wind 20 to 50 km/h. Treeline temperature -2 °C. Freezing level 500 to 1500 m.
Friday
A mix of sun and cloud with isolated flurries. South alpine wind 20 to 40 km/h. Treeline temperature -3 °C. Freezing level 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
Recent strong southerly winds have formed wind slabs on a variety of aspects in lee features in the alpine and treeline.
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 27th, 2023 4:00PM
