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Avalanche Forecast

Archived

Mar 10th, 2024–Mar 11th, 2024

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

As inputs of wind and snow become less intense Monday, we expect natural avalanche activity to diminish.

Human triggering remains a real concern: we have seen an alarming number of near-miss, human-triggered avalanches over the last week.

Stick to small low-angled slopes.

Avoid overhead avalanche terrain.

Confidence

Moderate

Avalanche Summary

Friday: a skier accidental avalanche occurred in steep treeline terrain. Explosive control on Mt Hector resulted in avalanches up to size 3 failing on both persistent and deep persistent layers.

Saturday: Sunshine Village Control triggered two cornices that pulled sz 2 slabs on the Feb 3 PWL in the fans. Elsewhere: a few small wet loose avalanches were observed in steep solar terrain and a few wind-triggered cornice failure and slab avalanches were reported in the alpine.

Snowpack Summary

New snow buries sun crusts found on steep solar aspects, and combined with elevated west winds, contributes to wind slabs as well as extensive wind effect in open alpine and treeline areas.

40-80 cm of settled snow overlies weak facets above the Feb 3 interface which is a crust up to 2500 m and higher on solar aspects.

The lower snowpack consists of several facet layers from January and December. Depth hoar and facets found at the base are weaker in shallow snowpack areas.

Weather Summary

Moderate to strong westerly winds will continue through Sunday night bringing up to 10cm of snow of a convective nature as freezing levels return to valley bottom.

Monday, winds will back off to light to moderate as the intensity of the precipitation tapers as well. Freezing levels are to rise to 1600-1800m.

For more detailed weather information, click here.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Remote triggering is a concern, watch out for adjacent and overhead slopes.
  • In times of uncertainty conservative terrain choices are our best defense.

Problems

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.

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.