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Avalanche Forecast

Archived

Mar 10th, 2023–Mar 11th, 2023

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 possible, human triggered probable.
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.

We are still wary of most steep terrain in the backcountry. Every day this week we've seen avalanche activity on the weak layers deep in the snowpack. Choosing moderate angled terrain with limited overhead hazard remains the best way to manage this snowpack.

Polar aspects should hold better skiing than sun exposed features at treeline and below.

Confidence

Moderate

Avalanche Summary

While natural activity has tapered off, we are still getting large whumpfs, and occasional natural and skier triggered avalanches on the deeper weak layers in the snowpack. A cornice triggered size 3 avalanche reported by Mt. Norquay ski hill in the last 48 hrs is the most recent.

Snowpack Summary

A sun crust is present on steep solar slopes at treeline and below, with 10-30 cm of soft snow on northerly aspects. The various Jan PWL interfaces of sun crusts, facets, and surface hoar are now down 40-80 cm. The weaker Nov. 16 basal facet layer is down 120-170 cm and still produces whumpfing and moderate to hard sudden collapse results in tests.

Weather Summary

A few cm's of new snow is expected Friday night with scattered flurries and a few sunny breaks on Saturday. Light W-SW winds with cool alpine temperatures of between -15 to -20°C are forecast.

For a more detailed weather forecast, click here.

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.