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Avalanche Forecast

Archived

Mar 9th, 2023–Mar 10th, 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're still wary of larger features in the backcountry. Everyday this week, we've seen natural activity on the persistent weak layers.

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

Confidence

Moderate

Avalanche Summary

While natural activity has tapered we're still seeing results on the deeper layers of the snow pack. Mt. Norquay ski hill reported a size 3 cornice failure within the last 24 being the most recent.

Likely triggers for natural avalanches are cornice failures and solar radiation and possibly both.

Snowpack Summary

Steep solar slopes at treeline and below are seeing the effects of the sun, with a significant sun crust in places. 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 produces moderate to hard sudden collapse results in tests.

Weather Summary

On Friday we should see the arrival of some snow, with flurries starting in the early afternoon. Southerly regions in the Park could see more snowfall with forecast amounts up 5 cm. Winds will pick up with strong gusts and temperatures will stay cold. An alpine high of -8 is being forecast.

Skies should clear Saturday, with light NW winds and only slightly warmer temperatures.

For a more detailed weather forecast, click here.

Terrain and Travel Advice

  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Uncertainty is best managed through conservative terrain choices at this time.

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.