Avalanche Forecast
Issued: Dec 11th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs and Wind Slabs.
AB,
Avalanche Canada
Yesterday, we transitioned the persistent slab into a deep-persistent slab problem and this will likely remain for some time. Conservative terrain choices are recommended.
Summary
Confidence
Avalanche Summary
Lake Louise ski patrol was able to trigger two size 2 avalanches with explosives today, both had fracture lines as deep as 50cm. Notably, a member of the Sunshine patrol triggered a size 2.5 (skier accidental, deep persistent slab) that was 60 meters wide and averaged 75cm deep. The bed surface was on the ground. The patroller was able to ski out to the side safely. Also, they produced many size 1 avalanches with ski cuts and explosives.
Snowpack Summary
Recent snow and moderate SW winds have formed wind slabs at higher elevations. In most other areas, 20-50 cm of snow is forming a soft slab over a very weak base of facets, with occasional thin crusts at the interface. Average snowpack depths at treeline are between 60 and 90 cm.
Weather Summary
Temperatures are expected to be relatively warm over the next few days with the alpine reaching -7 and the valley's close to zero. No significant precipitation will occur. Alpine winds are going to die down to the light range on Monday.
Terrain and Travel Advice
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- Uncertainty is best managed through conservative terrain choices at this time.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Deep Persistent Slabs
A 20-50 cm soft slab has formed over the very weak basal facets, with thin crusts at the interface in some locations. Human triggering is likely in steep terrain anywhere this slab is present, and whumpfing and cracking have been observed in many locations. Treat all steep terrain with caution. This problem will remain for the foreseeable future.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
10-25 cm of snow has fallen over the past several days with moderate S-W winds. This has formed soft wind slabs in lee areas. These slabs are relatively soft and small but still possible to trigger. The major concern is that if triggered, these may step down to the weak basal facets and result in larger avalanches.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 12th, 2022 4:00PM
