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Avalanche Forecast

Archived

Dec 29th, 2014–Dec 30th, 2014

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

Little Yoho.

Good skiing/boarding can be found in wind sheltered terrain. Continue to avoid steep or convex terrain especially if there are terrain traps below, and enjoy the good skiing on lower angled well supported slopes.

Weather Forecast

A cold night (-22C) tonight.  Warm air pushes into the region tomorrow creating an inversion with warmer air in the alpine.  For the next few days, expect a mix of sun and cloud, light winds, and highs of -7.

Snowpack Summary

Recent winds have created small wind slabs in the alpine which sit over the Dec 18 layer of crust, facets and/or surface hoar depending on the location. Surface hoar is more prevalent in the Little Yoho region and a poor bond exists at this interface. At the base of the snowpack weak crusts and facets exist which are still a concern.

Avalanche Summary

"Speed Run" at Lake Louise ran naturally as a size 2 on December 26th following some moderate wind transport overnight. On the 27th, skiers triggered a small slab in Wizard Chutes (Sunshine region) and it stepped down to the basal facets yeilding a size 2.5 avalanche. 

Confidence

The weather pattern is stable

Problems

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.