Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
Skiers and explosives continue to trigger the windslab and deep persistent problem layers. Stick to lower angle and well-supported terrain. Give the snowpack time to adjust to the recent loads.
Confidence
Moderate
Avalanche Summary
Although the peak of the cycle has passed, there have been more skier and explosive-triggered avalanches on Monday. Skiers triggered a size 2 windslab on the convex roll in Wawa bowl near Sunshine Ski area. Avalanche control on Mt. Dennis and Mt. Field on Monday produced results up to size 3. These avalanches failed at the ground in the deep persistent basal facets in terrain that had been previously controlled.
Over last weekend there were several notable avalanches. Bourgeau Left hand slid naturally (size 3). On Saturday there was a MIN report of a remote-triggered slide with wide propagation in the Sunshine backcountry. On Sunday, a visitor safety team also triggered a healthy size 2.5 (80 wide) at 2400m on observation glades and another party on Helen Shoulder triggered a size 2.
Snowpack Summary
Up to 40cm of recent storm snow in the North (10cm in the South) of the region has been redistributed by strong winds forming widespread, reactive windslabs. Two crusts exist in the upper snowpack and the November facets remain near the base. These buried weak layers remain a concern and continue to produce avalanches. Minimal reactivity has been observed below treeline.
Weather Summary
Tuesday, expect scattered flurries, more along the East slopes with up to 5 cm in some locations, and N-NW wind at 20-30 km/hr. Temperatures will range from -5 to -11 C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Make conservative terrain choices and avoid overhead hazard.
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avalanche Problems
Wind Slabs
Up to 10 cm fell in the past 24 hours (highest amounts near Bow Summit) creating fresh thin pockets of windslab over older reactive windslabs. These can be triggered by humans. In many areas these wind slabs overlay a variety of surfaces like crusts, or a firm mid-pack from previous wind effect with facets on top . There continue to be avalanches related to this problem and there have been many reports over the past few days.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2.5
Deep Persistent Slabs
There have been numerous natural and human-triggered avalanches on the basal facets and depth hoar recently. They are either initiating on this layer or more frequently initiating as a wind slab which steps down.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1.5 - 3.5