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Avalanche Forecast

Archived

Jan 30th, 2023–Jan 31st, 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.

Numerous wind slabs and the occasional deep slab has been the pattern over the last couple of days, and the next few days to come. Use good judgment and resist steep terrain as we come out of the cold weather.

Confidence

Moderate

Avalanche Summary

On Mt. Field, a size 2.5 natural deep slab was observed. It ran within 200m of the Kicking Horse River, occurring within the last 24 hours. A large cornice fell down which triggered a slab on Mt. Bosthworth, and the debris ran to mid-runout. Lake Louise patrol triggered two size 2 wind slabs that gauged down into facets with large explosives.

Snowpack Summary

Moderate to strong W-N winds have formed wind slabs at treeline and 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 variable sudden test results. In areas west of the divide, the snowpack is more supportive than in eastern areas.

Weather Summary

Warming temperatures which will bring things back to seasonal over the next two days. A trace of snow is expected on Tuesday. Winds will remain in the strong range from the West, Tuesday through Thursday.

More details can be found in the Mountain Weather Forecast

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.