Avalanche Forecast

Archived

Feb 7th, 2023–Feb 8th, 2023

Alpine

Natural and human triggered avalanches likely.

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.

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.

Fresh wind slabs are touchy in the Alpine and more snow and wind are on the way. Areas at treeline and above will see increased danger levels on Wednesday.

Confidence

Moderate

Avalanche Summary

Visibility was somewhat limited, but 2 fresh naturally triggered size 1.5 wind slabs were observed in the Alpine on east aspects immediately below ridgeline in the Burstall Pass area today.

Snowpack Summary

Up to 5cm of new snow fell in the past 24 hours, with lots of wind at upper elevations. Fresh wind slabs are found in the Alpine and open areas at Treeline. Forecasters observed cracking in their skin track today, but ski cutting produced minimal results. Having said that, 2 new naturally triggered wind slabs (size 1.5) were observed in the Alpine on east aspects. It seems that the Alpine has much more sensitive wind slabs, and these will continue to build over the next 24 hours. Snow profile at 2350m today reveals that the bottom 80cm of facets is actually gaining a bit of strength. While this is good, snowpack tests still indicate failures in the facets, and thinner/rockier start zones are still a major concern where the facets will be easier to trigger.

Weather Summary

Wednesday will be overcast with light flurries and highs of -8C. Snowfall amounts are uncertain with models predicting anywhere from 8 to 15+cm over the next 24hrs. Winds will be strong from the SW.

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.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.

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.