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Avalanche Forecast

Archived

Nov 30th, 2020–Dec 1st, 2020

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

Kootenay Boundary.

As the wind shifts northwest, watch for new wind slabs in unusual locations. 

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

Monday night: Clearing, moderate northwest wind, freezing level valley bottom.

Tuesday: Clear, light northwest wind, freezing level 500 - 1000 m with an above freezing layer developing 2500 - 3500 m in the late afternoon.

Wednesday: Clear, light southeast wind, freezing level 700 m with an above freezing layer 1500-3000 m.

Thursday: Clear, light southwest wind, freezing level 700 m.

Avalanche Summary

Explosive control work produced size 1-1.5 wind slab avalanches on Friday. We've not had any reports of avalanche activity since then.

Our eyes and ears in the mountains are limited at this time of year and may continue this winter due to fewer professional observations. If you see anything (or don't) while out in the field, please consider sharing via the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!

Snowpack Summary

Wind and small inputs of snow have formed wind slabs in on a variety of aspects at upper elevations. In more sheltered areas, recent snow may rest on a couple of layers of surface hoar 5-10 cm and 15-25 cm below the surface.

Treeline snowpack depths sit around 100 to 150 cm in the north and 50 to 100 cm in the south of the region. 

Melt-freeze crusts from mid- and early-November are generally found 30 cm below the snow surface and 30 cm up from the ground, respectively. While they are still showing results in snowpack tests, most reports indicate that the bonds at the interfaces with these crusts are improving.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Be aware of the possibility for full depth avalanches due to deeply buried weak layers.
  • Be cautious of buried obstacles especially below treeline.

Problems

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.

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.