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Avalanche Forecast

Archived

Feb 1st, 2022–Feb 2nd, 2022

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 possible, human triggered probable.

Regions

North Columbia.

Recently formed slabs will require some time to bond to the snowpack, particularly where they overly a widespread weak layer.

Confidence

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

Weather Forecast

TUESDAY NIGHT: Clear skies with no precipitation, 10 to 20 km/h north wind, alpine temperature -22 C.

WEDNESDAY: Increasing clouds with afternoon snowfall, accumulation 1 to 3 cm, 20 km/h southwest wind, alpine temperature -20 C.

THURSDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 20 to 40 km/h west wind, alpine temperature -12 C.

FRIDAY: Cloudy with snowfall, accumulation 10 to 20 cm, 40 to 60 km/h southwest wind, alpine temperature -7 C.

Avalanche Summary

Widespread avalanche activity was observed on Monday. They were mostly small to large (size 1 to 2.5) storm slabs, being triggered naturally, by riders, and explosives. They often failed on the surface hoar crystals described in the snowpack summary. For areas where the recent snow had not formed a cohesive slab, small loose dry avalanches were observed. 

A large explosive triggered the December 1 facet/crust layer described in the snowpack summary. The avalanche was at 1600 m in an opening, on a southwest aspect. It varied from 50 to 180 cm deep.

Looking ahead to the coming days, storm slab avalanches are expected to remain triggerable by riders as the recent snow settles and forms a cohesive slab above the widespread surface hoar layer.

Snowpack Summary

Around 30 to 60 cm of recent snow overlies weak surface hoar crystals 5 to 15 mm in size, which is most prominent in areas sheltered from the wind. The snow has consolidated and formed storm slabs in some areas, which is expected to remain touchy to riders for some time. In other areas, the snow remains uncohesive without slab properties. The snow overlies a melt-freeze crust on sun-exposed slopes. Expect to find wind slabs in lee terrain features at higher elevations.

A few other weak layers of surface hoar and faceted grains exist in the top metre of snow but are reported as hard to find.

The facet/crust layer that formed in early December is buried around 120 to 250 cm. The last reported avalanche was on January 31 from a large explosive, and before that on January 23. This is a low probability but high consequence problem. Check out the forecaster blog for more information.

Terrain and Travel

  • Good day to make conservative terrain choices.
  • Make observations and assess conditions continually as you travel.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.