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Avalanche Forecast

Archived

Dec 17th, 2022–Dec 18th, 2022

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

Regions

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

Be aware that if triggered, avalanches may step down to deeper layers resulting in large, destructive avalanches. Keep your terrain choices conservative and be prepared to back off quickly if you find signs of instability like whumpfing and shooting cracks.

Confidence

Moderate

Avalanche Summary

Avalanche activity in the region has tapered off during the week. Over the last weekend the mid November surface hoar layer was very reactive throughout the region as well as the rest of the Selkirks and Monashees. This layer will likely remain rider triggerable in specific sheltered terrain features.

Snowpack Summary

Recent clear periods have formed large surface hoar on sheltered slopes and a sun crust on south facing terrain.

A small layer of surface hoar from early December can be found down 30 to 50cm in sheltered and shaded terrain. On south facing slopes this layer is a thin crust.

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

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

Weather Summary

Saturday Night

Scattered flurries bringing up to 5cm of new snow. Light to moderate westerly wind. Low of -14 at 1500m.

Sunday

Scattered flurries bringing up to 5cm of new snow. Light to moderate southwest wind. High of -11 at 1500m.

Monday

A mix of sun and cloud with light flurries bringing trace amounts of new snow. Light to moderate west winds and temps falling throughout the day to -18 at 1500m.

Tuesday

A mix of sun and cloud with light flurries bringing trace amounts of new snow. Light to moderate southwest winds and a high of -15 at 1500m.

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.

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.

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.