Avalanche forecast

South Columbia

Jan 2 – 3, 2022Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

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.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Wind slabs will continue to build with light snowfall and winds over the day on north and east aspects. Strong south/southwest winds will create deeper deposits in wind loaded features, use caution approaching ridge crest and cross loaded features. 

    Reactive slabs are expected as new snow falls over weak crystals and wind effected surfaces. Larger avalanches could be triggered in the treeline where wind slab has formed over surface hoar.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–3.5

    Weak faceted grains above the early December crust continue to produce unpredictable results. Large destructive avalanches have been produced on this layer recently. This layer is found around 80 to 150 cm deep and is most common at elevations between 1700 m and 2400 m. Read more about it here.

    There is also a layer of weak surface hoar found about 25 to 50 cm deep, generally in terrain features sheltered from the wind. This layer may be more prevalent in the southern half of the region, creating more reactive conditions in sheltered terrain features. 

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.

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