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Avalanche Forecast

Archived

Dec 22nd, 2022–Dec 23rd, 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 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.

Regions

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

carefully assess each slope for wind slab. wind slab avalanches have the potential to step down to deeper layers.

Confidence

Moderate

Avalanche Summary

On Tuesday and Wednesday several size one skier triggered wind slab avalanches were reported. These avalanches were on easterly aspects at upper treeline.

Snowpack Summary

Variable winds mean that wind slab could be found on all aspects at treeline and above. These new slabs will form over facets, surface hoar or a crust meaning they will not bond well.

The snow becomes slightly more consolidated after the above mentioned layer until around 50cm below the surface where another weak layer, 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.

The snowpack is becoming increasingly complex and faceted.

Weather Summary

Thursday Night

flurries bringing up to 5cm of new snow. Light westerly winds and a low of -20 at 1800m.

Friday

Cloudy with up to 10cm of new snow expected. Westerly winds increasing throughout the day to strong . High of -15 at 1800m.

Saturday

Stormy with around 15cm of new snow expected. Strong southwest winds and a high of -6 at 1800m.

Sunday

Cloudy with trace amounts of new snow expected. Light to moderate westerly winds with a high of -6 at 1800m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.

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.