Avalanche Forecast

Archived

Dec 13th, 2023–Dec 15th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

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

We are likely to see a 5-10cm of new snow over the next 24 hours with moderate westerly winds. Be cautious for windslabs in alpine and treeline areas.

Confidence

Moderate

Avalanche Summary

A few small windslabs up to size 1 were observed in steeper alpine areas. These occurred on lee (N and E) aspects.

Snowpack Summary

Alpine terrain looks like a typical early December winter with many ridges blown free of snow and lee features containing windslabs. Treeline areas are much the same although some areas that are more protected have been spared from the recent strong westerly winds. Up to treeline expect to encounter a rain crust down 30-50cm that formed in an early December storm. So far failures on this crust have been few, but as it develops we expect this layer to become a common bed surface for avalanches. A surface hoar layer is also found up to treeline beneath this crust that was producing moderate results in snowpack tests. Deeper in the snowpack a weak basal layer persists that was a thin melt freeze crust in some areas, or just weak basal facets and depth hoar. Thin areas are still common places to trigger these windslabs which are likely to propagate across a feature so keep this in mind as you travel.

Be curious and dig into the snowpack! Share your observations on the MIN.

Weather Summary

A small front is expected to cross the region thursday with 5-10cm cm of snow fall expected. Winds will will be moderate out of the SW with temperatures around -2C as a daytime high.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Approach lee and cross-loaded slopes with caution.

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.

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.