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Avalanche Forecast

Archived

Jan 22nd, 2023–Jan 23rd, 2023

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

Regions

Kootenay Boundary, Bonnington, Kootenay Pass, Norns, Rossland, South Okanagan, Ymir, Moyie, St. Mary.

Wind slabs are developing at higher elevations

Large to very large avalanches continue to be produced from our complex snowpack.

Seek out low-angle terrain that has a deep snowpack to find the best and safest riding.

Confidence

Moderate

Avalanche Summary

Avalanche control work done on Friday produced very large (up to size 3.5) avalanches. These were from our persistent problem and deep persistent problem. Although fewer in number, Saturday's avalanches were of similar nature.

Under the right circumstances, riders can trigger these layers. Heavier loads like those created by smaller avalanches will trigger these deeper layers as well.

Snowpack Summary

At higher elevations, wind slabs are beginning to form from west and southwest winds. In sheltered areas surface hoar growth has been reported. The top 30 to 50 cm of snow contains a wide variety of layers that include, crusts, surface hoar, and facets. These layers have not yet produced widespread avalanches however, they are important to keep in mind as they vary with aspect and elevation as they still pose a hazard depending on your terrain choices.

Layers that are presently a concern include a surface hoar layer developed in early January and a melt-freeze crust from late December that is now down approximately 70 cm. These layers have created our persistent slab problem. The deep persistent slab problem stems from a weak layer created in mid-November and it is now buried 100 to 190 cm deep. These layers are a major concern and if triggered they can result in large avalanches.

Thank you for inputting your snowpack observations in the MIN. For more information on the state of the snowpack, click HERE.

Weather Summary

Sunday Night

Cloudy but clearing into the night, possible trace accumulation, 20 to 30 km/h west winds, treeline temperatures around -10 and -5 C.

Monday

Mostly cloudy with some sunny periods, trace accumulation, 20 to 35 km/h west winds, treeline temperatures around -5 C.

Tuesday

Cloudy with sunny periods, possible trace accumulation, 25 km/h northwest wind, treeline temperatures -7 C.

Wednesday

Mostly cloudy, no accumulation, 30 km/h northwest wind, treeline temperatures -4 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.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • 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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.