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Avalanche Forecast

Archived

Jan 27th, 2021–Jan 28th, 2021

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

Regions

Northwest Coastal.

Variable moderate winds may have formed fresh wind slab or soft slabs on Wednesday at all elevations. These slabs sit on a buried surface hoar layer and below 1000 m on a crust.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

WEDNESDAY NIGHT: Mainly clear, light variable wind, treeline temperatures around -16 C.

THURSDAY: Sunny, light westerly wind, treeline temperatures around -14 C. A mild alpine temperature inversion builds with warmer alpine temperatures than in the cooler valleys. 

FRIDAY: Mainly cloudy with scattered flurries, up to 10 cm new snow in the very south of the region, moderate south wind gusting strong, treeline temperatures around -14 C. A mild alpine temperature inversion persists.

SATURDAY: Mainly cloudy with scattered flurries, up to 10 cm new snow, moderate south wind, treeline temperatures around -12 C.

Avalanche Summary

On Tuesday, explosive control in the north produced a few small avalanches in recent snow. Isolated small and large slab avalanches have been reported to have failed on recently buried surface hoar or crust in recent days.  

In the northern regions (e.g. Stewart or Ningunsaw), large explosives were able to trigger a couple of very large avalanches on deep persistent layers near the ground last week. Debris are still evident from the widespread avalanche cycle over a week ago with size 1-3 storm slabs (in the south of the region) and size 3-4 deep persistent slabs (in the north of the region).   

Snowpack Summary

The 10-20 cm of new snow which fell over the weekend might have been transported with reverse eastern wind on Wednesday and formed fresh soft slabs and wind slabs. This snow sits on a crust below 1000m and surface hoar in sheltered locations at and below treeline. Cold clear temps are perfect for ongoing surface hoar formation and near-surface faceting, which will continue to soften older hard surfaces, develop facets around buried crusts and weaken cornices. 

A total of 100-150 cm of settled snow has fallen in January, which has helped strengthen early season weak layers. Deeper layers appear to have gone inactive in the southern part of the region. However, in the northern part of the region (e.g. Bear Pass, Ningunsaw) there has still been regular avalanche activity on weak snow at the bottom of the snowpack with large loads such as explosives or cornice collapses.

Terrain and Travel

  • Make observations and assess conditions continually as you travel.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Watch your sluff: it may run faster and further than you expect.

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.