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Avalanche Forecast

Archived

Dec 1st, 2024–Dec 2nd, 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 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.

Warm temps should make travel more pleasant but we are still dealing with a thin early season snowpack. The generally weak faceted snowpack means that even small avalanches could run further than expected as they entrain facets in steep terrain. The deep persistent layer remains a concern on large alpine slopes.

Confidence

Moderate

Avalanche Summary

Several small wind slabs were reported on lee slopes in the alpine over the weekend.

In the past week a few natural and explosive-triggered avalanches up to size 2 have been reported on the Oct deep persistent layer on north aspects in the alpine.

Sunday a couple size 1-1.5 explosive triggered slides were reported at Sunshine on the Nov crust on south aspects in the alpine.

These avalanches have been entraining facets and sometimes running further than expected as a result.

Snowpack Summary

In general, we are still dealing with an early-season snowpack, measuring 50-90 cm at treeline. Previous strong winds have created a heavily wind-affected upper snowpack in the alpine. A Nov crust is present mid-pack on south aspects. The main layer of concern remains the October crust near the ground on north aspects, where facets and depth hoar are developing. Overall, the snowpack is losing its support and cohesion due to facet development.

Weather Summary

Monday will see a clearing trend with moderate to strong winds out of the west. The gradual warmup will persist into the start of the week, with daytime highs reaching -3°C in the alpine by Tuesday.

Terrain and Travel Advice

  • Be aware of the possibility for full depth avalanches due to deeply buried weak layers.
  • Avoid freshly wind-loaded terrain features.

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.