Avalanche Forecast
Issued: Jan 15th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
Find the best riding in wind sheltered terrain above 2000 m but keep your guard up around steep pockets where storm snow may be settling over a fragile layer of surface hoar or a slippery crust.
Summary
Confidence
Weather Forecast
Friday night: Clear, light northwest ridgetop wind, freezing level valley bottom.
Saturday: Mix of sun and cloud, light northwest ridgetop wind, freezing level 600 m.
Sunday: Flurries, moderate northwest ridgetop wind, freezing level 800 m.
Monday: Sunny, light northerly ridgetop wind, freezing level 800 m.
Avalanche Summary
On Wednesday, a widespread natural avalanche cycle up to size 2.5 was reported. A recent MIN report observed from Rossland shows a size 3 natural persistent slab avalanche that occurred during or post-storm.
Last week, a naturally-triggered size 3 deep persistent slab avalanche released on a southeast aspect at 2200 m in the Rossland range. The avalanche likely failed on the weak layers described in the snowpack summary and scrubbed to the ground.
Snowpack Summary
A surface crust exists up to around 2000 m. The top 20-40 cm of the snowpack is composed of some elevation dependent permutation of a crust sandwich, formed by fluctuating freezing levels during the last storm. A layer of surface hoar (or another crust) may sit beneath the recent storm snow in sheltered terrain.
Two weak layers are buried in close proximity to one another. They are 70 to 130 cm deep. The layers are composed of surface hoar and faceted grains and they overlie a hard melt-freeze crust. This recent MIN report observed from Rossland on Wednesday the 13th shows good evidence of a large natural slab avalanche failing on the early December persistent layer during or post-storm. This suggests that it remains possible for riders to trigger these layers.
Another layer of faceted grains above a melt-freeze crust that formed in early November is upwards of 200 cm below the surface. This has been the suspected failure layer of a few very large avalanches that released last week in the Rossland range.
Terrain and Travel
- Be careful as you transition into wind affected terrain.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Wind Slabs
Previous wind has deposited recent snow into deeper slabs on leeward slopes at upper elevations. Wind slabs may remain reactive, particularly where they sit over surface hoar in sheltered terrain or a crust. Recent wind has varied in direction so watch for wind loading on a variety of aspects.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Weak surface hoar and/or faceted grains sit above a melt-freeze crust around 80 to 130 cm deep. The likelihood of triggering a persistent slab has reduced, but the consequence of doing so remains high.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 16th, 2021 4:00PM
