Avalanche Forecast

Archived

Dec 24th, 2020–Dec 25th, 2020

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 unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Regions

Kananaskis.

Merry Christmas! Winds were strong on Thursday and we saw widespread new windslabs develop and in some places fail, triggering the deeper basal layers. These upper snowpack instabilities are definitely skier triggerable. Be conservative in your choices!

Confidence

High -

Weather Forecast

Well the winds were howling on Thursday but they are forecast to begin to back off a bit on Friday. Winds on Friday will be more moderate out of the SW with day time highs in the -6C range. No new precipitation is expected as we will be under the influence of a high pressure ridge until the 26th when we are expecting to get some new snow.

Avalanche Summary

A few large avalanches were observed over the past 24hrs failing down up to as much as 2m on the November crust. One of these large slides was likely triggered by a cornice collapse. In addition to these large events, there were numerous windslabs up to sz 2 failing in steeper alpine features mainly on N and E aspects.

Snowpack Summary

Strong winds is the main thing to talk about with regards to the snowpack. Winds over the past 24hrs have been strong out of the SW and most alpine areas have been highly affected. In some areas we are seeing windslabs overloading the basal November crust triggering large avalanches that are running to the valley floor. Expect to encounter windslabs at open areas at treeline and expect the windslabs to fail in steep or crossloaded areas down 40-60cm at the Dec 8th interface.

Terrain and Travel

Avoid steep convex slopes.
Back off steep and aggressive lines, stick to simple terrain.
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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.