Avalanche Forecast

Archived

Jan 27th, 2023–Jan 28th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

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

5-15cm of storm snow fell over the past 24hrs with light winds from the north. A few cms more snow may fall overnight but amounts are not expected to be significant. Thinly covered snowpack areas are now harder to see.

Confidence

Moderate

Avalanche Summary

A few loose dry avalanches at treeline and below up to size one. One isolated sz 1 windslab in an alpine feature near Mt Chester.

Snowpack Summary

On average 10cm of new snow fell at treeline with some areas seeing more and some a bit less. Valley bottoms (where snow is needed the most) was where it was less with only around 5cm accumulation. This new snow is overlying a thin melt freeze crust up to 2100m but so far the bond appears to be good. The upper snowpack continues to strengthen with the only notable sheer at the interface with the deeper weak facets in the moderate range. Isolated windslabs were observed in alpine areas on southern aspects from the recent northerly winds but they do not extend far downslope.

As the snowpack above the weaker base becomes more cohesive the potential for wide propagation increases. This will be a common theme this winter and you should always be thinking about consequences of an avalanche.

Weather Summary

A surface ridge of high pressure over Alberta will keep conditions cold with daytime highs around -21C. Expect mainly cloudy skies with light flurries across the Rockies with the help of some northeasterly upslope flow. Unfortunately the storm is over and what remaining flurries we are expected to get, won't accumulate too much. Winds will be in the moderate range out of the NW.

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.