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Avalanche Forecast

Archived

Jan 31st, 2023–Feb 1st, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Numerous natural wind slabs and the occasional deep slab avalanche have been the pattern over the last couple of days and the next few days to come. Use good judgment and resist being lured into or near steep terrain.

Confidence

Moderate

Avalanche Summary

Over the past few days, there have been reports of numerous windslab avalanches to size 2, cornices failures triggering avalanches, and deep persistent avalanches to size 3. On Tuesday, Sunshine patrol triggered a size 2.5 avalanche with explosives released on the ground in the deep persistent layer. In the past few days, in Yoho, a deep persistent slab avalanche was observed on Mt. Carnarvon (size 3) and on Mt. Field (size 2.5). The Mt. Field avalanche ran to within 200m of the Kicking Horse River. The Mount Lefroy avalanche also scrubbed to ice in some locations.

Snowpack Summary

Moderate to strong W-N winds have formed wind slabs at treeline and in the alpine. Below this, the upper snowpack contains weak layers 20-40 cm deep (Jan. 4th) and 30-60 cm deep (Dec. 17th) that are generally unreactive. The Nov 16 deep persistent layer is down 40-90 cm and continues to produce variable sudden test results. In areas west of the divide, the snowpack is more supportive than in eastern areas.

Weather Summary

Expect strong Westerly winds for the next few days. Some light flurries start Wednesday morning with up to 5-10 cm expected along the Continental Divide and west. Alpine temperatures will be in the -10 to -15C range for Wednesday and -5 to -10 C range for Thursday and Friday.

More details can be found in the Mountain Weather Forecast

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.