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Avalanche Forecast

Archived

Dec 19th, 2022–Dec 20th, 2022

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

Regions

Kootenay Boundary, Bonnington, Grohman, Kootenay Pass, Norns, Rossland, Ymir, Moyie, St. Mary, Kokanee, Retallack, Valhalla.

Manage your terrain and keep an eye out for the persistent slab problem as you enjoy the fresh snow.

Signs of instability like whumpfing and shooting cracks are a clear indication to back off for the time being.

Confidence

Moderate

Avalanche Summary

No new avalanches reported in the last 24 hours other than some minor sluffing.

Avalanche activity is tapering off what it was last week when the mid-November layer was very reactive, producing large avalanches in our region and that of our neighbours'. This layer should still be a concern and can be triggered in areas with a shallow snowpack or in certain terrain such as convex rolls.

Snowpack Summary

The top 10 to 25 cm of our snowpack is of low-density unconsolidated snow that sits on a buried surface hoar layer in sheltered areas and a sun crust on the solar aspect. The snow becomes slightly more consolidated after these layers until 35 to 45 cm below the surface is reached where another weak, created in early December, can be found. This layer is made up of surface hoar in sheltered areas and a thin sun crust in open south-facing terrain.

The layer that is still the main concern, is that of mid-November. It is made up of large surface hoar crystals, facets, and a melt-freeze crust and can be found up to 80 cm deep. This layer has been reactive at treeline between 1700 to 2200 m, on all aspects.

Below the mid-November layer is a generally weak, faceted snowpack. Snowpack depths average 80 to 160 cm in the alpine.

Weather Summary

Monday Night

Cloudy with clear periods, no accumulation, 10 to 20 km/h southwest wind, -22 C at 1500 m.

Tuesday

Mostly cloudy, up to 13 cm accumulation, 15 km/h south winds, -21 C at 1500 m.

Wednesday

Mostly sunny with cloudy periods, no accumulation, 15 to 22 km/h northeast wind, temperature -25 C at 1500 m.

Thursday

Sunny, no accumulation, 10 km/h south winds, -23 C at 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Don't let the desire for deep powder pull you into high consequence terrain.
  • If triggered, loose dry avalanches may step down to deeper layers resulting in large avalanches.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.