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Avalanche Forecast

Archived

Nov 28th, 2024–Nov 29th, 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.

The winds have increased and are forecasted to get stronger, we are a little uncertain as to the extent and reactivity of the fresh windslabs. We also may see some loose dry activity with the increased wind in extreme terrain.

The Oct crust deep persistent problem remains the layer of greatest concern on large alpine slopes.

Confidence

Moderate

Avalanche Summary

No new avalanches were observed or reported today. In the Sunshine region, a natural size 2 avalanche on the deep persistent layer was observed on Thursday on an alpine North aspect in extreme terrain and two days prior on Scarab Peak. Over the past few days, there have been reports of deep slab avalanches with explosives at both Sunshine and Lake Louise ski hills.

Snowpack Summary

10-20 cm of snow from last week lies on an early-season snowpack measuring 50-90 cm at treeline. Two weak layers are present: the November 9 crust, found 25-40 cm above the ground, and an October crust near the ground, where facets and depth hoar are developing. Observations of the October layer are limited, but it appears most prominent on northerly aspects at treeline and above.

Weather Summary

Low of -13C and highs of -7C Friday. Westerly winds increase to strong by mid-day Friday and continue into Saturday with very light flurries. See image below for tables.

Terrain and Travel Advice

  • Be aware of the possibility for full depth avalanches due to deeply buried weak layers.
  • Wind slabs are most reactive during their formation.
  • 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.