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Avalanche Forecast

Archived

Feb 7th, 2022–Feb 8th, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Cariboos.

Human triggered avalanches that release on the buried weak layer keep surprising skiers and riders. The uncertainty on where and if this layer can be triggered is best managed with conservative terrain choices.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

MONDAY NIGHT: Clear with cloudy periods, up to 3 cm new snow, light to moderate west wind, alpine temperature -4 C, freezing level 600 m.

TUESDAY: Cloudy, up to 5 cm new snow, light southwest wind, alpine temperature -2 C, freezing level 1400 m. 

WEDNESDAY: Cloudy, 10 to 15 cm new snow, light southwest wind, alpine temperature 0 C, freezing level rising to 2100 m. 

THURSDAY: Sunny with cloudy periods, up to 3 cm new snow, light to moderate southwest wind, alpine temperature +2 C, freezing level 2500 m.

Avalanche Summary

On Sunday, two natural large avalanches of size 2-2.5 were observed in steep terrain on north and east aspects in the alpine. Several large avalanches released on sun exposed steep slopes. Riders triggered a large size 3 avalanche in the south of the region.

On Saturday, several storm and wind slab avalanches up to size 2.5 were observed at treeline and in the alpine. Most released naturally, and a couple were likely triggered by riders. Skiers triggered a large avalanche remotely in the south of the region (see this MIN report for details - thank you for the report).

Observations on Friday were limited due to bad visibility. A natural avalanche cycle of small storm slab avalanches up to size 1.5 was reported.

Snowpack Summary

The recent storm brought around 30 to 50 cm of snow. The snow formed wind slabs in lee terrain features from strong southwest wind and storm slabs in wind sheltered areas.

The snow will be particularly touchy where it loaded a weak layer of surface hoar crystals. This layer is likely anywhere from 50 to 100 cm deep. Reports suggest that the surface hoar is most prominent in sheltered openings at and below treeline but could extend into wind-sheltered terrain in the alpine. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns. On south aspects, a melt-freeze crust may exist instead of surface hoar.

The lower snowpack is generally strong and well-bonded.

Terrain and Travel

  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Uncertainty is best managed through conservative terrain choices at this time.

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.