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Avalanche Forecast

Archived

Dec 12th, 2024–Dec 13th, 2024

Alpine
Natural avalanches unlikely, human triggered possible.
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.
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.

Field teams over the last couple of days have noted a big difference between snowpacks west of the divide and those east of the divide. Although it is still thin at lower elevations in both areas, the snowpack is much thicker and more confidence inspiring at treeline and above if you are in a thicker, western area.

Confidence

Moderate

Avalanche Summary

Lake Louise threw a bunch of explosives with minimal results today. Over the past few days, similar explosives have triggered isolated wind slabs and a number of deep persistent avalanches.

Snowpack Summary

Windslabs exist in exposed and wind-prone alpine. In sheltered areas, soft snow sits on a layer of facets, suncrust and isolated surface hoar. Below this, the midpack is thin, weak in eastern regions, and deeper and denser in areas west of the divide. Two crust/facet layers exist near the bottom of the snowpack (Nov. 9th and Oct. 20th interfaces). Total snowpack depths at treeline are generally 60cm in eastern areas with up to 100 cm in thicker western areas

Weather Summary

Light winds, treeline temperatures around -8C, and only a trace of snow for Thursday. See image below for more details.

Terrain and Travel Advice

  • Be careful with wind-loaded pockets, especially near ridge crests and rollovers.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid thin areas like rocky outcrops where you're most likely to trigger avalanches on deep weak layers.

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.