Avalanche Forecast

Archived

Mar 2nd, 2023–Mar 3rd, 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 unlikely, human triggered possible.

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

Some light snow and moderate winds will likely keep the danger elevated Friday. It is March, but forecasters have little faith in the snowpack given the deeper weak layers.

Confidence

Moderate

Avalanche Summary

Lake Louise ski hill reported explosive-triggered size 1 stiff wind slabs, and smaller natural avalanches in steep, unsupported terrain. Also, semi-circular bowl (Lake Louise ski hill backcountry) slid naturally. It was reported as a size 2 with no information about what type of layer it slid on.

Snowpack Summary

Wind slabs are present in the alpine and at treeline. These wind slabs overlie the various Jan PWL interfaces of sun crusts, facets, and surface hoar down 80-120 cm. The weaker Nov. 16 basal facet layer is down 100-200 cm and produces moderate to hard sudden collapse results. Deeper snowpack areas west of the divide are stronger and more supportive than areas to the east.

Weather Summary

30-50km/h winds and convective flurries (2-5cm) Thursday night into Friday AM.

Friday: During the day, expect another few cm over Western slopes with ridgetop SW winds at 30-40km/h. Alpine temperatures will be in the -5 to -10C range with freezing levels at valley bottom.

Saturday: A weak upper ridge with weakening SW winds (20-30km/h) will give way to cloudy skies and flurries with light winds shifting to the East.

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.

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.