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Avalanche Forecast

Archived

Jan 1st, 2022–Jan 2nd, 2022

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

Regions

South Columbia.

Avalanche danger will increase over the day as strong winds continue to form reactive slabs over a weak snow surface. Approach wind loaded features with caution.

Confidence

Moderate - Uncertainty is due to the track & intensity of the incoming weather system.

Weather Forecast

An active front moves south over BC bringing strong winds ahead of snowfall that begins late Sunday afternoon.

SATURDAY NIGHT: Continued light snowfall, 2-5cm with strong to extreme southwest winds. 

SUNDAY: Moderate southeast winds increase over the day to strong southerlies. 5-15cm possible over the day. Alpine high of -15. 

MONDAY: 5-10cm of snow, tapering off in the afternoon. Alpine high of -10 with light southerly winds.

TUESDAY: Chance of flurries with light southeast winds. Alpine high of -15. 

Avalanche Summary

Numerous natural and human triggered slabs have been reported since Wednesday to size 2, from 10-40cm deep. These occurred in wind effected features on all aspects due to the recent variable winds. Cornice failure has been noted in several cases to have triggered the wind slab below. Cornices are able to effect deeply buried weak layers, navigate around them (on ridgelines, and on slopes below them) with care. Additionally, several slabs were thought to have failed on a buried surface hoar layer.

Several large and destructive avalanches have been naturally and skier triggered in the Selkirks over the last week up to size 3.5. Each had wide propagation and ran several hundred metres. The avalanches were up to 250cm deep and were triggered in a rocky and thin area. This layer is still extremely concerning and will likely be for most of the season.

We'd appreciate if you submit your observations to the Mountain Information Network, even just a photo.

Snowpack Summary

New snowfall and wind continues to redistribute recent snow into deeper deposits on north and east aspects at treeline and above. These new slabs will form over faceted and wind effected surfaces, creating a poor bond and reactive slabs. 

A layer of weak surface hoar crystals can be found 30-50cm deep in sheltered terrain features at alpine and treeline elevations, and in open features like cut blocks below treeline. 

The crust formed by the early December rain event sits 100-150cm deep and is found up to 2400m in the South Columbia's. Weak and faceted grains sit above, creating a weak interface that is still reactive to human triggers. This layer is most reactive at treeline, and in areas where the snowpack thins and the weak interface is much closer to the surface. This layer has the potential to produce large and destructive avalanches if triggered. Recent activity in the Columbia's has been limited to explosive triggers - however the southern Selkirks have seen significant skier triggered activity on this layer to size 3.5.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.

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.