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Avalanche Forecast

Archived

Dec 16th, 2022–Dec 17th, 2022

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

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 largesurface hoar on sheltered slopes and a sun crust on south facing terrain. AS the winds change to a northerly direction it is likely that wind slab will be found on all aspects in exposed terrain at treeline and above.

A small layer of surface hoar from early December can be found down 30 to 40cm 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

Friday Night

Cloudy with the possibility of light flurries bringing trace amounts of new snow. Moderate to strong northwest winds shifting to west in the morning with a low of -14 at 1800m.

Saturday

Scattered flurries bringing up to 5cm of new snow. Light to moderate westerly wind. High of -13 at 1800m.

Sunday

Scattered flurries bringing up to 5cm of new snow. Light westerly wind. High of -13 at 1800m.

Monday

Mostly cloudy with light flurries bringing trace amounts of new snow. Light southwest winds and a high of -15 at 1800m.

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.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.

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.