Avalanche Forecast

Archived

Feb 24th, 2025–Feb 25th, 2025

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

The snowpack is gradually adjusting to the new load from the recent storm. While minimal natural avalanche activity has been observed since the storm, several human-triggered avalanches have been reported over the past two days. Conservative terrain choices will be the best risk mitigation strategy over the next few days.

Confidence

Moderate

Avalanche Summary

The local ski hills reported triggering several avalanches today using explosives and ski cuts, up to size two. One notable observation was a ski cut that initiated a size 2 deep persistent slab, 1 meter deep.

A skier accidental size 2 wind slab that likely propagated on the facets under the storm snow was observed on Twin Cairns Sunday, with one person going for a rocky ride but ending up relatively unscathed.

Snowpack Summary

10-30 cm of new snow has fallen with mild temps and strong S-SW winds helping to form new wind and storm slabs. This new snow sits over a layer of weak facets, surface hoar or sun crust from the cold snap.

The mid-pack is generally weak facets, while depth hoar and crusts form an even weaker base. The snowpack is the weakest in eastern areas where snow depths are low. In these areas, the basal weaknesses should be carefully considered.

Weather Summary

A southwest flow may bring light flurries to the forecast region on Tuesday, with snow accumulation ranging from 0 to 5 centimeters by Wednesday. Ridgetop winds are expected to be moderate, coming from the W-SW. Daytime high temperatures will be around +5°C at the valley bottom on Tuesday.

Terrain and Travel Advice

Make conservative terrain choices and avoid overhead hazard.
Avoid freshly wind-loaded features, especially near ridge crests, rollovers, and in steep terrain.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Loose avalanches may step down to deeper layers, resulting in larger 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.