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Avalanche Forecast

Archived

Dec 22nd, 2020–Dec 23rd, 2020

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.

Regions

Kananaskis.

Pull in the reins! Lots of new snow, but hazard is high. Human triggering of avalanches is very likely.

Confidence

Moderate -

Weather Forecast

Wednesday should be mainly sunny with a brisk -20c to start the day. Temperatures should rise to near -11c with winds out of the north in the light to moderate range. No new snow is expected.

Avalanche Summary

Observations have been somewhat limited by poor visibility, but an avalanche cycle is occurring. Numerous slabs and loose dry avalanches up to size 2.5 have occurred in the past 24 hours. These are occurring at all elevations and on all aspects.

Snowpack Summary

40 to 50cm of snow fell in a very short period of time, which has overloaded the snowpack. Winds were strong out of the north during the storm, so expect widespread wind slabs at Treeline and above. The Dec 8th layer of surface hoar/crust/facets remains on the radar, especially with this new load. The Nov rain crust is now deeply buried in the snowpack, and while it hasn't been reactive recently, it could easily wake up with the new snow load. Field observations were very limited today, and forecasters will be going out with eyes wide open on their next field day - the snowpack has experienced significant change!

Terrain and Travel

  • Avoid steep convex slopes.
  • Back off steep and aggressive lines, stick to simple terrain.
  • Make conservative terrain choices and avoid overhead hazard.
  • Be cautious of sluffing.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.

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.

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.