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Avalanche Forecast

Archived

Jan 14th, 2021–Jan 17th, 2021

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

Regions

Waterton Lakes.

Wednesday's storm has formed widespread wind slabs at upper elevations, and a breakable crust below treeline. Choose moderately angled terrain with low consequence, avoid walking under cornices, and travel downhill through the burnt forest with care.

Weather Forecast

Friday: Cloudy with sunny periods and an alpine inversion. Strong to Extreme W winds, alpine high 0 early in the morning dropping to -5 in the afternoon

Saturday: Mainly cloudy with isolated flurries. Moderate NW winds, inversion with alpine high of -5

Sunday: Cloudy with flurries. Inversion breaking down during the day, with strong to extreme W wind

Snowpack Summary

The storm brought 30cm of new snow. Upper elevations are heavily wind affected, and new windslabs will be found in lee areas. Below 1900m rain during the storm formed a breakable crust which can be found under 5cm of fluff. The Dec 9th crust can be found down 70-100cm at Cameron Lake. Areas east of the divide hold a thin & faceted snowpack.

Avalanche Summary

Good visibility on Thursday showed a widespread avalanche cycle in most wind loaded features from Size 1 to Size 3 that occurred on Tuesday night/Wednesday morning. A couple of these involved step down avalanches to deeper weak layers, including a size three with impressive propagation in  a thin convexity in Rowe Bowl.

Confidence

The weather pattern is stable

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.