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Avalanche Forecast

Archived

Dec 18th, 2022–Dec 19th, 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, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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

Buried weak layers remain reactive to triggering.

Signs of instability like whumpfing and shooting cracks are a clear indication to back off and go with your 'Plan B.'

Confidence

Low

Avalanche Summary

No new avalanches reported in the last 24 hours. This was not the case earlier this past week. The mid-November surface hoar layer was very reactive throughout our region and in the rest of the Selkirks and Monashees. This layer will likely remain rider triggerable in specific sheltered terrain features.

Snowpack Summary

From Saturday night to Monday morning, 15 to 30 cm will have fallen throughout our region. This has buried a surface hoar layer that can be found on sheltered slopes and a sun crust on south-facing terrain. A small layer of surface hoar from early December can be found down 35 to 60 cm in sheltered and shaded terrain. On south-facing slopes, this layer is a thin crust. At this writing, neither of these layers has shown reactivity but that is likely to change with the addition of a slab on top of this layer.

A weak layer of large surface hoar crystals, facets, and a melt-freeze crust from mid-November sit 50 to 80 cm deep. This layer has been reactive at treeline between 1700 to 2200 m, on all aspects producing large remotely triggered avalanches.

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

Weather Summary

Sunday Night

Cloudy, 2 to 5 cm accumulation, 10 to 20 km/h west wind, -20 C at 1500 m.

Monday

Sunny, no accumulation, 15 km/h northwest winds, alpine temperature of -25 C.

Tuesday

Cloudy with sunny breaks, up to 5 cm accumulation, 15 km/h southeast wind, temperature -20 C at 1500 m.

Wednesday

Sunny, trace accumulation, 20 km/h northeast winds, alpine temperature of -25 C.

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.