Avalanche Forecast

Archived

Jan 1st, 2022–Jan 2nd, 2022

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

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 possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Lizard-Flathead.

Avalanche danger will rise towards the end of the day as the next storm blows in. Check out the latest Forecasters' Blog for tips on managing the persistent slab problem in this region.

Confidence

Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather. Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Saturday night: Mostly cloudy. Moderate southwest wind. Alpine temperature around -15 C.

Sunday: Flurries starting in the afternoon, around 5 cm. Moderate to strong southwest wind. Alpine high of -9 C.

Monday: 10-20 cm new snow. Strong southwest wind. High of -7 C.

Tuesday: 10-20 cm new snow. Light to moderate southwest wind. High of -8 C.

Avalanche Summary

On Friday, wind slabs were reactive to explosives up to size 1.5. On Thursday, small (size 1) natural and artificially triggered wind slabs were reported in the alpine.

A few surprisingly deep older crowns were observed between Fernie and Sparwood on Friday. These suspected persistent slab avalanches likely ran on the early December crust around the same time as the explosive triggered size 3 persistent slab reported on December 27th.

Snowpack Summary

Variably wind affected surfaces can be found at upper elevations, including soft to hard wind slabs on a variety of aspects.

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 80-150 cm. Activity on this layer has been sporadic, most recently reported on December 27th. Since then, snowpack tests have produced no results but we remain wary. This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.

Terrain and Travel

Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
Be aware of the potential for large avalanches due to the presence of a persistent slab.
Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.