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Avalanche Forecast

Archived

Mar 2nd, 2025–Mar 3rd, 2025

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

Regions

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

While cooling is expected to end the widespread natural avalanche cycle on Monday, the likelihood of human-triggering the persistent slab this week remains less certain.

Caution is still advised on slopes that do not exhibit a surface crust, which can be expected to be largely unaffected by last week's heating.

Confidence

Moderate

Avalanche Summary

This weekend, widespread slab avalanches were observed on steep, solar-exposed terrain entraining wet snow at lower elevations to sz 3. Several cornice failures were also reported at local ski resorts, triggering persistent slabs up to size 2.5.

Avalanche Control:

Saturday - Mount Whymper - 12 shots = 12 slabs sz 2.5-3.5 on the Jan 30 layer

Sunday - Simpson and Wardle - 13 shots = 14 slabs sz 1.5-3 mainly persistent slabs however a few stepped down into midpack or basal layers

Snowpack Summary

10 to 30 cm of snow fell last week on a weak layer of facets, surface hoar, or sun crust. Extreme west winds and warm temperatures have encouraged slab formation (and created solar crusts). Previous slabs, another 10 to 30cm thick sit on a similar weak layer (Jan 30).

The midpack is weak and faceted everywhere while depth hoar and crusts form an even weaker base in eastern areas where snow depths remain low. In these areas, the basal weaknesses should be carefully considered.

Weather Summary

A weak low moved into Alberta Sunday evening. Light NE winds will bring upslope snowfall and cooling.

A few cm of snow is expected overnight in eastern areas, with another 5cm reaching areas further west Monday as the low is pushed by a ridge forming behind it in Alberta. Up to 10cm is expected in total before winds shift back west Tuesday bringing clearing

Terrain and Travel Advice

  • Keep in mind that human triggering may persist as natural avalanches taper off.
  • A hard crust on the snow surface will help strengthen the snowpack, but may cause tough travel conditions.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.