Avalanche Forecast

Archived

Dec 29th, 2022–Dec 30th, 2022

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 possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Jasper, Brazeau, Churchill, Cirrus-Wilson, Fryatt, Icefields, Maligne, Marmot, Miette Lake, Pyramid.

The deeper weak layers are active and human-triggered avalanches are likely. A special avalanche warning has been issued which includes our region.

Be extra cautious in wind affected areas where a stiffer slab can propagate widely.

Confidence

Moderate

Avalanche Summary

Avalanche Control along the Icefields Parkway on Thursday produced several large slab avalanches in wind loaded tree line slopes. These slides were triggered as winds slabs and stepped down to ground with wide propagation. Below tree line slopes produced small slab avalanches running at the storm snow interface.

Numerous natural avalanches up to size 2.5 were also observed in the alpine along the Icefields Parkway.

Snowpack Summary

20-30 cm of recent storm snow has developed into a slab over the December 17th facets. Alpine and tree line slopes are heavily wind affected. Facets and depth hoar make a weak base in most areas. Snow height ranges from 50-120cm.

Weather Summary

Overnight Thursday and through the day Friday, the forecast calls for mainly cloudy skies, light flurries, and moderate winds from the southwest. Temperatures steady around -10.

Terrain and Travel Advice

Make conservative terrain choices and avoid overhead hazard.

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.