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Avalanche Forecast

Archived

Jan 17th, 2020–Jan 18th, 2020

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

Regions

Cariboos.

Variable wind directions and a blanket of new snow mean that wind slabs could be triggered in exposed terrain.

Confidence

Moderate - Uncertainty is due to limitations in the field data.

Weather Forecast

FRIDAY NIGHT: Increasing clouds, light southwest wind, alpine temperature -18 C, freezing level below valley bottom.

SATURDAY: Cloudy with snowfall, accumulation 5 to 10 cm, moderate to strong southwest wind, alpine temperature -12 C, freezing level below valley bottom.

SUNDAY: Cloudy with light snowfall, accumulation 2 to 5 cm, moderate to strong southwest wind, alpine temperature -7 C, freezing level below valley bottom.

MONDAY: Cloudy with snowfall, accumulation 5 to 10 cm, moderate to strong southwest wind, alpine temperature -5 C, freezing level 1200 m.

Avalanche Summary

Avalanche activity has quieted down over the past few days, but light snowfall and southwest switching to northeast wind are likely refreshing the wind slab problem. A rise in air temperature in the coming days may increase slab properties in the recent snow.

Last weekend there were notable signs of a reactive persistent slab problem, including large whumpfs and a large snowmobile triggered avalanche in the neighbouring Clemina area (see the MIN report). The surface hoar layer responsible for this problem has been harder to find since then, but could still potentially produce large avalanches in certain sheltered slopes around treeline. The likelihood of triggering this layer could increase as the air temperature rises.

Snowpack Summary

Surface conditions are variable due to the recent cold temperature and variable wind directions. Fresh wind slabs are likely present on exposed slopes at and above treeline.

The main concern over the past week has been a layer of surface hoar buried 60-120 cm beneath the surface. Although an avalanche has not been reported on this layer in the past four days, the likelihood of triggering it may increase as new snowfall accumulates and stresses it.

Terrain and Travel

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Be aware of highly variable recent wind loading patterns.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.

Problems

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.

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.