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Avalanche Forecast

Archived

Dec 26th, 2022–Dec 27th, 2022

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 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.

Mt. Stephen will be closed on Tuesday, Dec 27 for avalanche control - no climbing or skiing there. Strong SW winds, warm temperatures and 20-30 cm of recent snow have combined to make dangerous avalanche conditions with widespread, new windslabs bonding poorly to the underlying snowpack. Seek out sheltered locations to find the best quality and most stable snow.

Confidence

Moderate

Avalanche Summary

Not many observations today due to the poor visibility, but several size 1.5 windslab avalanches were reported by ski hill avalanche control teams and observed on the fans above Crowfoot Trees.

Of note to ice climbers, Bourgeau left-hand went sz 2.5 within the last 48-hours.

Snowpack Summary

Strong to extreme westerly winds at upper elevations have blown 20-30 cm of recent HST into widespread, windslabs susceptible to human triggering. This problem sits atop a layer of facets and surface hoar buried on Dec 17, but any avalanche of note that starts may step down to the deeper persistent layers near the ground. Cooling temperatures later this week should provide a minor improvement.

Snow profile at Crowfoot Trees.

Weather Summary

The active weather continues on Tuesday with another 5-10 cm expected. The strong winds will taper through the day on Tuesday and overnight into Wednesday with some cooling temperatures by mid-week. More stable weather is expected later this week (Thurs/Fri).

Terrain and Travel Advice

  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Uncertainty is best managed through conservative terrain choices at this time.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.