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Avalanche Forecast

Archived

Jan 21st, 2016–Jan 24th, 2016

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

Regions

Waterton Lakes.

Friday is not the day to be pushing your limits. Stick to easily managed terrain. Conditions will improve by late in the weekend, but start small and build up, evaluating conditions critically as you go. 

Weather Forecast

Strong-Extreme SW winds until Friday evening. A classic chinook...expect the highest windspeeds and freezing levels in the East of the Park. Temperatures may reach 5 degrees in town, and an Above Freezing Layer makes an appearance at treeline early Friday. 5-15cm of new snowfall by Friday evening. The weekend: cooler temperatures and light winds.

Snowpack Summary

Fresh wind slabs are building lee to Moderate - Strong SW winds, sitting atop harder, thicker wind slabs from strong SW winds several days ago. Down 40-50cm is a weak layer: Sun crust on solar aspects, and surface hoar on most non-solar slopes. This layer is producing mainly Moderate-Hard shears. Tests indicate limited propagation potential.

Avalanche Summary

Poor visibility is hampering avalanche observations. Cornices have grown, but proved stubborn to triggering when cut by forecasting staff at treeline elevation ridges. Cornice chunks and ski cutting produced only thin surface Wind Slab results in immediate lees and unsupported features, however areas of thicker buried Wind Slab were avoided.

Confidence

Due to the number of field observations

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.