Avalanche Forecast

Archived

Mar 27th, 2023–Mar 28th, 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 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.

Solar input on Tuesday could be a trigger for natural avalanche activity. Choose low angle slopes and avoid overhead terrain.

Confidence

Moderate

Avalanche Summary

Nothing new was observed today, but observations were limited.

Several loose dry size 1-1.5 avalanches on all aspects occurred on Sunday in extreme unskiable terrain.

Several slab(30-40cm thick) avalanches size 1.5-2 occurred on Sunday on East to South aspects. This is likely on the March 12 facet/surface hoar/crust interface.

Snowpack Summary

As much as 40cm of recent snow has settled down to about 25cm overlying a variety of previous surfaces. So far there has been very little wind effect to the recent snow and it is staying dry on polar aspects. However, solar aspects have now seen several generations of sun crust, and this recent snow will become moist by late morning on Tuesday. Forecasters are tracking 3 main weak layers in the snowpack. First, a buried sun crust on solar, or a layer of facets on polar aspects, are producing some natural and human-triggered avalanches down between 20 and 40cm. Second, a weak layer formed back in late January has occasionally been active down 80 to 100cm. A very large human-triggered avalanche occurred on this layer late last week. And finally, the basal weaknesses remain. Deep persistent slab avalanches are still possible, especially in shallow snowpack areas. This deep layer may also be prone to "waking up" as slopes start to get more significant solar input. Forecasters continue to have zero confidence in larger terrain features, and we continue to avoid significant overhead terrain.

Weather Summary

It will be a cold start on Tuesday with temperatures dropping to the -20C range! The late March sun will pack a punch and it should be mostly clear skies with highs reaching -4C by the afternoon. The winds are expected to be light from the NW with no new snow expected.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Minimize exposure to sun-exposed slopes when the solar radiation is strong.
In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Minimize exposure to steep planar south-facing slopes - especially if they see sunshine.

Problems

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.

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.