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Avalanche Forecast

Archived

Nov 24th, 2024–Nov 25th, 2024

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely.
Below Treeline
Below Threshold.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely.
Below Treeline
Below Threshold.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Below Threshold.

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Winds are expected to increase on Monday. Stay alert for increases in localized wind slab development and snow transport, as well as potential for failures on the Oct crust/facet layer.

Recent snowfall has improved skiing conditions at higher elevations, though it's important to remain cautious of rocks and hidden hazards.

Confidence

Moderate

Avalanche Summary

Ski hills reported several size 1-2 avalanches triggered by explosives including loose dry slides and a few slabs on the Oct crust/facet layer near the ground. These slabs were on northerly aspects above 2400 m like other recent results.

One skier accidental on the Oct crust/facets was reported at Bow Summit.

A couple of natural size 2 cornice triggered slabs were observed in steep alpine terrain on Mt Brett and Monarch and both appeared to fail on the Oct crust/facet layer.

Snowpack Summary

10-20 cm of low-density storm snow with some wind effect developing, sits over an early-season snowpack ranging from 50-90 cm deep at treeline. Two weak layers exist: a Nov 9 crust layer 25-40 cm above the ground, and an Oct crust just above the ground with facets and depth hoar developing around the Oct crust. We have limited observations of how widespread this Oct layer is, but it seems to be most prominent at treeline and above on northerly aspects.

Weather Summary

Scattered flurries with minimal snow accumulation are expected to continue across the forecast region. Ridge-top winds will increase on Monday into the moderate range from the west. Temperatures will stay cool with treeline highs around -12 to -14°C.

This pattern is expected to last through Tuesday, with cooling temps and a little bit of snow on Wednesday.

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.
  • Be careful with sluffing in steep terrain, especially above cliffs and terrain traps.

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.