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Avalanche Forecast

Archived

Jan 31st, 2022–Feb 1st, 2022

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

Regions

North Columbia.

New slabs have formed, which sit on a widespread weak layer. Conservative terrain travel is recommended.

Confidence

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

Weather Forecast

MONDAY NIGHT: Cloudy with snowfall, accumulation 1 to 3 cm, 20 to 30 km/h west wind, alpine temperature -14 C.

TUESDAY: Cloudy with snowfall then clearing, accumulation 1 to 3 cm, 20 to 30 km/h northwest wind, alpine temperature -17 C.

WEDNESDAY: Increasing clouds with afternoon snowfall, accumulation 1 to 3 cm, 20 to 40 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 -13 C.

Avalanche Summary

Many storm slabs and loose avalanches were triggered by riders on Sunday within the recent storm snow. The avalanches were most reactive where they sat on the surface hoar layer described in the snowpack summary.

Looking forward, human-triggering of avalanches may remain elevated, particularly where the recent snow overlies surface hoar.

Snowpack Summary

Around 30 to 50 cm of snow fell on the weekend with strong wind, forming new storm slabs in sheltered terrain and wind slabs in exposed terrain. These slabs overly a widespread layer of weak surface hoar crystals that was reported as 5 to 15 mm in size, most prominent in terrain sheltered from the wind. The snow overlies a melt-freeze crust on sun-exposed slopes.

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. Although the last reported avalanche was about a week ago, the snowpack structure remains and it 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.