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Avalanche Forecast

Archived

Dec 16th, 2022–Dec 17th, 2022

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 unlikely, human triggered possible.
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.

More snow and wind will keep the avalanche hazard elevated this weekend. A deep freeze is on its way with temperatures dropping down to the - 30s by Sunday. Be prepared for the unexpected with extra warm clothing.

Confidence

Moderate

Avalanche Summary

Over the past few days, both ski hills have triggered deep slabs up to size 2 with explosives or sometimes with a ski cut after the explosive failed to trigger the slope. Parks Forecasters have noted large whumphs in the Sunshine Backcountry on Tuesday and in the O'hara region on Thursday. No new naturals have been observed for the past few days.

Snowpack Summary

20-60 cm of snow has formed a slab over a very weak base consisting of facets. Thin crusts can be found on the facet interface at lower elevations and on solar slopes. Snowpack depths at treeline range between 60 and 120 cm. Below treeline, small sluffs may be triggered in steep features where the ski and foot penetrations are to the ground in a very weak facetted snowpack,

Weather Summary

A surface ridge of high pressure will continue to push moist air South causing upslope conditions on the Eastern slopes of the Rockies. We could see up to 10cm of low-density snow in the forecast region by Sunday. The temperature will drop through the day Saturday with alpine lows temps to -30. Increased winds and new snow will add to the loading in the alpine , likely developing new slab at upper elevations.

Terrain and Travel Advice

  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Uncertainty is best managed through conservative terrain choices at this time.

Problems

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.

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.

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.