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Avalanche Forecast

Archived

Dec 4th, 2024–Dec 5th, 2024

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.
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.

With clear skies and warm temps, be mindful of the potential for wet loose avalanches out of steep solar aspects.

Some fresh wind-slabs can be expected in immediate alpine lees.

Keep the deep persistent layers in mind, especially on large alpine slopes.

Confidence

Moderate

Avalanche Summary

Lake Louise ski hill had a few explosive results Wednesday during avalanche control operations. Mainly no results but some size 1 wind-slabs on NE aspects in the alpine with one more significant result with an larger explosive trigger size 1.5 on a deeper persistent weak layer.

Sunshine ski hill reported some solar triggered natural size 1's out of steep rocky terrain at ridgetop.

Snowpack Summary

The early-season settling snowpack at treeline measures 50-90 cm. In the alpine there is scouring on windward slopes and some fresh loading on immediate lee aspects. A surface crust or moist snow may exist on steep south aspects below 2500m. The November crust lies mid-pack on south aspects, while the main concern is the October crust near the ground on north aspects, where facets and depth hoar are forming. The snowpack is generally weak and facetted.

Weather Summary

Freezing levels Thursday will continue to climb (up to ~1900m) as there will be reduced cloud cover and a warm air mass moves into the region. Winds will continue to be moderate to strong from the west. Friday temps will cool with some forecasted precipitation Saturday.

Terrain and Travel Advice

  • Rocks will heat up with daytime warming and may become trigger points for loose wet avalanches.
  • Pay attention to the wind; once it starts to blow, sensitive wind slabs are likely to form.
  • Be mindful that deep instabilities are still present in the 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.

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.