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Avalanche Forecast

Archived

Nov 21st, 2024–Nov 22nd, 2024

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

Regions

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

Recent snowfall has improved the skiing at higher elevations. Watch for rocks and hidden hazards.

The Oct 23 layer may become more reactive to skier traffic with increased load.

If the wind picks up, then keep and eye out for windslabs and sluffing.

Confidence

Moderate

Avalanche Summary

Sunshine had one explosive result on Nov 20th, a size 2 cornice release into Delirium Dive.

Over the past week several avalanches have released with explosive triggers on the Oct 23 layer on North-East aspects. A few size 1 explosive results on the Nov 9 crust but no new windslabs.

Snowpack Summary

10-30 cm of low density storm snow sits over an early season snowpack ranging from 50-90 cm at TL. Two weak layers exist: a Nov 9 crust/surface hoar 25-40 cm above the ground, and an Oct crust/facet layer right above the ground. Avalanches have been failing on the Oct crust in alpine areas with explosives at Lake Louise ski hill. We have limited observations of how widespread this layer is, but we think the Oct crust is more prominent at treeline and above on Northerly aspects.

Weather Summary

The "bomb cyclone" is continuing to weaken and move offshore with an Arctic cold front descending from the north and out on to the prairie. Friday, winds will remain light with precipitation around 5cm, overcast skies and seasonal temperatures.

Terrain and Travel Advice

  • Pay attention to the wind; once it starts to blow, sensitive wind slabs are likely to form.
  • Avoid steep terrain, including convex rolls, or areas with a thin, rocky, or variable snowpack.

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.