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Avalanche Forecast

Archived

Dec 17th, 2023–Dec 18th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
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 possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.

Regions

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

Consistently strong winds remain the theme in the alpine and at treeline. Be wary of any wind loaded slopes, and watch for wind loading at upper elevations. Wind slabs also have the potential to step down to the basal weak layer resulting in larger avalanches.

With the short days, get out early and get home early.

Confidence

No Rating

Avalanche Summary

A large natural avalanche was observed in the alpine on Mount Fairview on Friday. Additionally, there have been natural, human and explosive triggered avalanches at the Lake Louise and Sunshine ski hills up to size 2 within the last few days. Wind slab has been the primary avalanche problem, however there are still avalanches stepping down to the deep persistent weak layer at the base of the snowpack.

Snowpack Summary

Wind slabs continue to build in alpine and exposed treeline areas with mod-strong SW winds. In isolated areas at treeline these slabs may be sitting on the Dec 14 surface hoar. Below this is 20-40 cm of snow from early Dec. This includes a rain crust up to 7 cm thick that exists as high as 2300 m, and is more prevalent in the south part of the forecast area. The base of the snowpack is a mix of surface hoar, basal facets and a crust from late Oct. Treeline snow depths range from 50-90 cm.

Weather Summary

Monday will bring a mix of sun and cloud with possible light flurries west of the divide. Ridgetop winds will increase into the moderate to strong range out of the southwest on Sunday night and stay elevated through Monday.

The alpine high is forecast at -3°C and freezing levels will remain at valley bottom.

For more information, click Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.

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.