Avalanche Forecast
Issued: Nov 27th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
ahanna,
Avalanche Canada
Watch for recently formed wind slabs at upper elevations and be aware of the potential for larger avalanches due to a crust that was buried in early November.
Summary
Confidence
Weather Forecast
Friday night: 5-10 cm new snow, strong southwest wind, freezing level 1200 m.
Saturday: Clearing, wind easing to light west, freezing level 1000-1200 m.
Sunday: Clear, light southerly wind, freezing level 1000 m with an above freezing layer 1800-2400 m in the south of the region.
Monday: Sun and cloud, moderate southwest wind, freezing level 1800 m, 2000 m in the south.
Avalanche Summary
In the south, size 1-1.5 loose dry avalanches were observed in recent storm snow running on a melt-freeze crust in steep south-facing terrain on Wednesday.
In the north, large (size 2) storm slab avalanches were triggered naturally and by explosives on Wednesday near Duffey Lake. They occurred on northerly aspects in alpine terrain. The most recent report of an avalanche on the early-November layer was from November 21 near Duffey Lake. Check out this MIN for a photo.
Our eyes and ears in the mountains are limited at this time of year and may continue this winter due to fewer professional observations. If you see anything while out in the field, please consider sharing it with us and fellow recreationists via the Mountain Information Network (MIN). Even just a photo of where you went is helpful. A big thank you to those that have already shared their observations thus far.
Snowpack Summary
Recent new snow and strong southwest wind have produced wind slabs in lee terrain features at higher elevations.
The snowpack is characterized by a few crusts formed during warm periods over the last month.
- In the south of the region, where treeline snowpack depth sits around 100-150 cm, the deeper crusts are generally well bonded to surrounding snow. The topmost crust, which was acting as a slick bed surface for storm snow avalanches a few days ago, may be improving with the mild temperatures.
- In the north, treeline snowpack depth sits around 80 to 120 cm. The crust of note here is sitting near the base of the snowpack, likely surrounded by a weak layer of sugary facets. Snowpack tests and recent avalanche activity suggest that this layer could be triggered by humans and produce large avalanches.
Terrain and Travel
- Be careful as you transition into wind affected terrain.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Be cautious of buried obstacles especially below treeline.
- Uncertainty is best managed through conservative terrain choices at this time.
Problems
Wind Slabs
Recent snow and strong southwest wind have formed wind slabs in lee terrain features at higher elevations.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
In the north of the region (e.g., Duffey Lake), there is potential to trigger a weak layer of sugary faceted grains around a hard melt-freeze crust near the base of the snowpack. The last skier-triggered avalanche on this layer was last weekend. The most likely terrain features of concern are where the ground cover is smooth, such as on scree slopes, rock slabs, or glacial ice.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Nov 28th, 2020 4:00PM
