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Avalanche Forecast

Archived

Feb 22nd, 2023–Feb 23rd, 2023

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

Regions

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

We are coming out a large avalanche cycle, as cold weather has curbed the amount natural activity. Human triggering is still likely.

Confidence

Moderate

Avalanche Summary

Today we saw continued evidence of the natural cycle in the last 24/48h, with multiple naturals up to size 3 out of all aspects in the alpine.

Bombing today in the 93S area today produced results up to size 2.5, with the failure plane being the recent storm interface.

Snowpack Summary

Up to 80 cm's of storm snow over the several days has begun to settle into windslabs in the alpine, treeline and into the below treeline region. These slabs have been formed primarily by north and east winds. Expect them in places you may not normally see them. While becoming less reactive to human triggering, they can still be sensitive. There are crusts in the middle of the snow pack and the base of the snowpack is still weak with basal facets. Test profiles done today are still producing sudden results in the basal facets.

Weather Summary

We're in the middle of the cold snap. Alpine temperatures will remain in the -25 to -30 range, with wind chill to -40 in exposed areas! Cloudy skies with some flurries expected in the morning, giving way to clearer skies in the pm. Thursday evening into Friday morning will be the coldest time of this cold snap. Not a good night to be caught out!

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Make conservative terrain choices and avoid overhead hazard.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Cornice failure may trigger large avalanches.

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.

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.