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Avalanche Forecast

Archived

Dec 28th, 2020–Dec 29th, 2020

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

Regions

Cariboos.

Recent large human triggered avalanches failed on a very weak layer of surface hoar down 30-40 cm. and the sensitivity of this layer was described as "electric"! This layer has been found to be most prevalent at treeline and below in the areas surrounding Valemount.

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

  

MONDAY NIGHT: Partly cloudy / Moderate, northwest ridgetop wind / alpine low temperature -14 / Freezing level valley bottom.

TUESDAY: Mix of sun and cloud / Light, west ridgetop wind / alpine high temperature -10 / Freezing level valley bottom.

WEDNESDAY: Cloudy with isolated flurries; 3-5 cm. / Moderate, southwest ridgetop wind / alpine high temperature -8 / Freezing level valley bottom.

THURSDAY: Cloudy with flurries; 5-10 cm. / Light, west ridgetop wind / alpine high temperature -8 / Freezing level valley bottom.

Avalanche Summary

On Sunday, skier triggered and skier remotely triggered persistent slab avalanches up to size 2.5 on north aspects at treeline and below treeline were reported just northwest of Valemount. These avalanches failed on a very weak layer of surface hoar down 30-40 cm. and the sensitivity of this layer was described as "electric"! This layer has been found to be most prevalent in the areas surrounding Valemount.

Data in this region is very sparse. Please submit your observations to the Mountain Information Network. 

Snowpack Summary

Winds blowing from a variety of directions last week formed wind slabs in lee features at treeline and above.

An active weak layer is now down 30 to 70 cm. The distribution of this layer is variable. In some areas it's surface hoar and/or a crust; in others this layer may be difficult to find if it exists at all. Recent human triggered avalanches have been reported on this layer and have been most numerous in the areas surrounding Valemount.

There is a prominent crust near the base of the snowpack. This crust likely has weak facets above and/or below it. There have been no recent avalanches reported on this layer, but would be most likely to trigger in steep, shallow, rocky terrain, with a thin to thick snowpack.

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • 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.