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Avalanche Forecast

Archived

Nov 27th, 2022–Nov 28th, 2022

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

Regions

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

Uncertainty remains with how the new snow will contribute to the likelihood of triggering persistent slabs, that were already overlying a weak base.

Confidence

Moderate

Avalanche Summary

Lake Louise ski area triggered a size 1.5 wind slab with explosives in a high alpine lee pocket. Otherwise no avalanches were observed or reported.

Snowpack Summary

Up to 20cm of new snow has accumulated in the last 3 days, less so in valley bottoms. Windy conditions has promoted wind slab development in the alpine. The snowpack below these slabs is a mix of facets, spotty surface hoar, and sun crust on steep south aspects. 40-80 cm of total snow exists at treeline throughout the region, with up to 120 cm in loaded alpine features.

Weather Summary

Dropping temperatures and clearing skies into Monday. -20 at the ridge and -15 in valley are expected. The wind will also decrease into the light range from the North.

https://avalanche.ca/weather/forecast

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.