Avalanche Forecast

Archived

Feb 17th, 2023–Feb 18th, 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 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.

A few cms of snow over the past few days is adding up to around 10cm at treeline. This snow is adding load to the windslabs that formed earlier in the week. The snowpack still has an overall weak structure and a weak base and big features should be avoided.

Confidence

High

Avalanche Summary

One new sz 2.5 Slab was observed south of Black prince on Friday that ran full path but did not fail to ground. A few other small slabs were also observed and a few loose dry slides up to sz 1.

Snowpack Summary

10cm of snow fell at treeline on Friday with light winds from the west. This new snow is overlying a temperature crust on solar aspects up to 2400m throughout the range. Treeline and alpine windslabs continue to be the main avalanche concern in terms of "triggerability". They are improving with the the relatively warm temperatures, but still expect to find reactive pockets in steep and/or convex terrain. In terms of consequence, the dreaded Nov 5 facets still have a firm grip on the low probability/high consequence title. Some of our neighbours to the west have seen failures on this layer, which suggest that new snow loading or a wind slab trigger is a critical factor for when this layer will fail.

Weather Summary

Overnight on Friday the light flurries will continue and day time temperatures on Saturday will be around -8C. Winds will initially be strong out of the west and decrease throughout the day.

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.