Bulletin d’avalanche

South Columbia

Jan 3 – 4, 2022Avalanche Canada
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Archivé · expiré 5 years ago

Danger d’avalanche

Wed
Thu
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

New snow and wind will form touchy storm slabs at all elevations. Keep terrain selection conservative until the storm snow gains strength.

In localised areas that receive more than 30cm of new snow, avalanche danger will be HIGH.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–3.5

    Weak faceted grains above the early December crust continue to produce unpredictable large destructive avalanches. This layer is found around 80 to 150 cm deep and is most common concerning at treeline elevations. Terrain management skills are essential in dealing with this problem - avoid exposure to large unsupported slopes and thin and rocky start zones. This layer will be an ongoing issue this season. Read more about it here.

    A layer of weak feathery surface hoar is buried 40-60cm in wind sheltered terrain, still reactive to skier triggers. This layer may be more prevalent in the southern half of the region. Take care in cut blocks and sheltered openings at treeline and below. 

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    1–2

    Storm slabs will build with continued snowfall over the day. 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 sheltered treeline terrain features where slabs are forming over surface hoar.

Confidence

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

Weather Forecast

SUNDAY NIGHT: Strong southerly winds. 5-10cm possible overnight. Locally heavy accumulations are possible around Revelstoke, with up to 20cm overnight. 

MONDAY: Up to 5-10cm of snow, tapering off in the afternoon. Alpine high of -8 with light southwest winds.

TUESDAY: Chance of flurries with light southerly winds. Alpine high of -12. 

WEDNESDAY: Clearing skies, isolated flurries. Light southwest winds. Alpine high of -15. 

Avalanche Summary

Slabs in wind loaded features continue to be reactive to human triggers, producing avalanches up to size 2, on all aspects from the recent variable winds. As snowfall accumulates on top of these slabs they will be harder to identify. 

Cornice falls have triggered numerous slabs this week, as they land on the slope below. Navigate around cornices carefully (both on ridgelines and on the slopes below them with care - they are able to effect deeply buried weak layers. 

Several large and destructive persistent slab avalanches have been naturally and skier triggered in the Selkirks over the last week up to size 3.5, failing on the early December crust/facet interface. Each had wide propagation and ran several hundred metres. The avalanches were all 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

Storm snow with strong south-southwest winds continue to form new slabs with deeper deposits on north and east facing slopes. This load will be deposited on weak and wind effected surfaces - expect a poor bond and reactive conditions. 

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. 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

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • As the storm slab problem gets trickier, the easy solution is to choose more conservative terrain.
  • Avoid convexities, steep unsupported terrain and rocky outcroppings.

Régions couvertes