Avalanche Forecast

Archived

Dec 30th, 2022–Dec 31st, 2022

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely.

Regions

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

The upper snowpack is settling into a more cohesive unit due to light winds and warming temps overlying the weak facetted crystals that comprise the bottom of our snowpack. Thin areas will be the common trigger points.

Confidence

High

Avalanche Summary

A few thin avalanches up to sz 2 below corniced ridges within the recent snow were observed in the Burstall pass region. Visibility was limited in other areas.

Snowpack Summary

Forecasters were in treeline aras today and found by 2100m the Boxing Day melt freeze crust had generally disappeared. What we did find was the 1217th surface hoar, facet layer was down 40-50cm and producing moderate sudden collapse (anything sudden is bad). These results were more pronounced the higher we got in the treeline where the upper snowpack had seen more wind and was buried deeper. Thin areas are still very weak and the closer you are to these areas the more likely you are to get a collapse in the weak facets at the base of the snowpack. These weak facets towards the base of the snow pack will be a concern for some time unfortunately so always keep "full depth avalanches" in the forefront of your mind. We were playing it conservative today and encourage others to do the same. LIght snowfalls throughout the day with only a few cms of accumulation.

Weather Summary

Saturday at 4AM: Flurries continue across all regions in connection with a slow moving impulse over British Columbia. West winds are forecast to be 30 to 40 km/h. Freezing levels are expected to remain at or near valley bottom in all locations,

Saturday at 4PM: Although flurries will continue across the Alberta Rockies, they should taper off by morning as an upper ridge begins to build in. Additional snowfall amounts will be limited to a trace. Steady west-northwest winds in the 30-40 km/h range continue. Freezing levels will return to valley bottom overnight at all locations.

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 aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.