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Avalanche Forecast

Archived

Jan 3rd, 2021–Jan 4th, 2021

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 possible, human triggered probable.
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.

Regions

Kootenay Boundary.

Recently formed storm slabs will be most reactive in wind affected areas at treeline and above. Be especially cautious as you transition into wind affected terrain. 

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Sunday night: Scattered flurries, moderate southwest wind, freezing level 600 m.

Monday: Snow, 5-10 cm, moderate to strong south wind, alpine high temperature near -3, freezing level 1300 m.

Tuesday: Sun and cloud, moderate southwest wind, alpine high temperature near -7, freezing level 1000 m.

Wednesday: Snow, 5-10 cm, moderate southwest wind, alpine high temperature near -3, freezing level 1200 m.

Avalanche Summary

Numerous natural, human and explosive triggered storm slabs size 1-2.5 were reported on Saturday and Sunday. Check out this avalanche triggered remotely by a skier in Kootenay Pass on the weekend.

With new snow slowly but steadily piling up, the chances of a resurgence of persistent slab avalanches will increase. This incremental loading will likely make it difficult to predict when this layer may once again reach a tipping point and start producing avalanches. This problem is best managed with conservative terrain selection.

Snowpack Summary

30-60 cm of recent storm snow has seen significant wind affect at upper elevations. In sheltered areas, the recent snow may sit over surface hoar.

Two weak layers are buried in close proximity to one another. They are 70-100 cm deep around Nelson and 50-80 cm deep around Rossland and other western parts of the region. The layers are composed of feathery surface hoar and sugary faceted grains and they overlie a hard melt-freeze crust. 

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be especially cautious as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.