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Avalanche Forecast

Archived

Mar 25th, 2023–Mar 26th, 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, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Unstable air has brought convective flurries to the forecasting region over the last couple of days.

Expect bouts of both cloudy skies with intense snowfall and poor visibility, as well as sunny skies that can yield moist snow very quickly.

Human triggering of the persistent and deep persistent layers remains the main concern.

Confidence

Moderate

Avalanche Summary

No new avalanches were observed or reported Saturday.

Snowpack Summary

5-15 cm of snow fell March 24 to bury temperature crusts to 1600m, sun crusts to ridgetop on solar aspects and facets on shaded slopes.

The middle of the snowpack holds several crust and facet layers.

The base of the snowpack is weak, unconsolidated depth hoar in almost all areas.

Cornice failures occur regularly at this point of the season.

Weather Summary

Cloudy skies will start to clear into Sunday morning with the potential for a few flurries giving way to the potential for sunshine in the afternoon. Cloud will re-build overnight Sunday, again with the potential for flurries. Freezing levels will reach 1500m Sunday with further cooling for Monday. Alpine winds will remain light Sunday but may just touch into moderate on Monday.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

Problems

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.

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.