Avalanche Forecast

Archived

Dec 23rd, 2022–Dec 24th, 2022

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

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

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Kananaskis, Bow Valley, Highwood Pass, North 40, Spray - KLakes.

Southwesterly winds and temps will increase on Saturday making human triggered avalanches more likely. Models differ on snow amounts over the next few days but we may see between 10-40cm of snow by boxing day. This will be the first test of the weak facetted base layers.

Confidence

Moderate

Avalanche Summary

One new sz 2 avalanche was observed in Tent Bowl today that failed at 2700m on a NE aspect right at ridgeline in 40 deg terrain. The depth of the avalanche was only 30-40cm, 30m wide but the slide stepped down to ground and ran 200m

Snowpack Summary

At treeline snowpack depths vary based on orientation to the winds. On average 110cm of snow is found at this elevation. The main concern is the Late November interface down 55cm that is failing as a sudden collapse in snowpack tests. Beneath this layer the snowpack is weak and facetted.

Overall the weak facetted base persists everywhere in the region. As soon as there is a cohesive layer over this weak base the potential for human triggering will increase. The cohesion is most likely due to winds as you reach treeline. Any avalanche that occurs (even if it initiates in the upper snowpack) is likely to step down to the weak basal facet layers and involve the entire snowpack.

As winds and temps increase over the next 48 hours, we expect the snowpack to become more sensitive to triggerring so choose conservative areas like we have been saying.

Weather Summary

Temperatures are set to begin to increase over the next few days as the high pressure ridge that dominates the area begins to finally break down. As always, as temperatures rise up towards zero, winds will also increase... Expect winds to increae into the strong to extreme range out of the SW over the next 24hrs. In terms of snowfalls, models differ with regards to amounts Some models are calling for 40cm by boxing day while others are only calling for 5cm. So, as the system moves closer to our area pay attention to weather updates. Its safe to assume our current snowpack is weak and best and winds and snow are likely to push us towards an avalanche cycle.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Be especially cautious as you transition into wind affected terrain.
Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.

Problems

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.

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.