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Avalanche Forecast

Archived

Jan 27th, 2023–Jan 28th, 2023

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

Regions

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

Arctic air will bring cold temperatures to the forecast region this weekend. Be prepared with extra warm gear, as even a minor setback could become very serious in these temperatures.

Confidence

Moderate

Avalanche Summary

Both ski hills reported new soft slab development in the alpine that was reactive to ski cutting. No results were bigger than size 1. One natural avalanche size 1.5 was reported from the Lake Louise backcountry, this occurred during a short period of Strong wind values Friday morning.

Snowpack Summary

10 to 15cm of new snow Friday with little new wind effect overlays wind slabs in the alpine. Below this, the upper snowpack contains weak layers 20-40 cm deep (Jan. 4th) and 30-60 cm deep (Dec. 17th) that are generally unreactive. The Nov 16 deep persistent layer is down 40-90 cm and continues to produce sudden test results. In areas west of the divide, these layers are generally deeper and more spread apart in the snowpack.

Weather Summary

A ridge of high pressure will build Friday, bringing clear skies and colder temperatures for the weekend. As the cooling trend begins, we will see a 20-degree shift, with temperatures near -25°C by Saturday morning. Ridge winds will be in the moderate range Saturday and increase to strong by Sunday.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.

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.