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Avalanche Forecast

Archived

Dec 9th, 2019–Dec 12th, 2019

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

Regions

Waterton Lakes.

Increasing winds will continue to build slabs in the alpine and treeline. Approach wind affected terrain with care.

Weather Forecast

Tuesday: Cloudy with isolated flurries and an inversion with alpine highs of -2. Moderate to strong west winds.

Wednesday: Cloudy with isolated flurries with inversion breaking down and an alpine high of -7. Moderate west winds reaching strong to extreme overnight.

Thursday: Cloudy with flurries, alpine high of -5. and strong west winds.

Snowpack Summary

15-25cm storm snow coupled with moderate west winds has formed new slabs in the alpine. This overlies previous windslabs and a crust below 1800m. A melt freeze crust facet combo formed at the start of the season sits at the bottom of the snowpack. Though unlikely to be triggered by people, we have seen other avalanches stepping down to this layer.

Avalanche Summary

Saturday night's snowfall brought enough snow and wind to trigger a limited avalanche cycle in lee alpine terrain along the Akamina Parkway. In two cases these stepped down to early season weak layers on east aspects in the alpine. No new avalanches observed in the less snowy front ranges.

Confidence

Due to the number and quality 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.