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Avalanche Forecast

Archived

Nov 26th, 2024–Nov 27th, 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.
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.

As of Tuesday, wind slabs were minimal, even in the alpine. The key question for Wednesday is which wind forecast will materialize. Lower wind speeds will result in fewer wind slabs, while higher winds will lead to more. Pay close attention to local conditions and monitor carefully.

Confidence

Moderate

Avalanche Summary

The Sunshine Patrol reported another size 2 deep slab triggered by explosives in Delirium Dive. Similarly, Lake Louise Patrol triggered a size 1.5 deep slab in ER 5. See accompanying photo for details.

Snowpack Summary

10-20 cm of recent storm snow 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

Temperatures are expected to remain seasonal, with valley highs around -5°C and ridge temperatures near -12°C tomorrow. While some models hint at a few centimeters of snow on Wednesday, significant accumulation is unlikely. The primary concern is the wind, which could reach over 40 km/h from the west, though some models indicate lower speeds.

Terrain and Travel Advice

  • Be aware of the possibility for full depth avalanches due to deeply buried weak layers.
  • Pay attention to the wind; once it starts to blow, sensitive wind slabs are likely to form.

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.