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Avalanche Forecast

Archived

Dec 27th, 2020–Dec 28th, 2020

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

Regions

Jasper.

Conservative terrain choice is key until the reactivity of avalanche problems and their location can be deduced.

Weather Forecast

Monday: Cloudy with sunny periods. Precipitation: Nil. Alpine temperature: High -10 C. Ridge wind west: 10 km/h.

Tuesday: A mix of sun and cloud. Precipitation: Nil. Alpine temperature: Low -16 C, High -7 C. Ridge wind west: 10-20 km/h.

Snowpack Summary

15-30cm of soft snow or dense wind-slabs location dependent over a generally firm mid-pack. Dec. Surface Hoar is down 40cm in isolated sheltered spots and reactive to skier traffic. An early season crust is down 40-100cm and decomposing. It overlies basal facets and depth hoar but is well bridged by the mid-pack above unless shallow location.

Avalanche Summary

Sz 2 wind slab at 2000m on a NE aspect running far near the Saskatchewan Crossing yesterday. Surface hoar reactive to skier loads in isolated sheltered location up to 2000m.

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.

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.