Avalanche Forecast

Archived

Mar 28th, 2023–Mar 29th, 2023

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.

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.

Solar input will be a significant factor on Wednesday leading to a rapid destabilization of the snowpack on solar aspects. A good day to start early and finish early. Non-solar aspects have also had some large skier and naturally triggered avalanches in the past 24 hours. Check out this MIN for photos of the skier-triggered slide in Miner's Gully,

Confidence

Moderate

Avalanche Summary

A skier triggered size 2.5 slab avalanche occurred in Miner's Gully sometime Tuesday morning. Parts of the avalanche look to have steeped to ground. It is unknown if skiers were taken down with the slide, or if they remained on top, but it appeared to be a fairly major close call. This avalanche occurred on an East aspect at 2300m.

A size 3 naturally triggered deep persistent slab occurred in the past 24 hours on a North aspect at 2700m in the Goat Range. This avalanche exhibited wide propagation.

A size 3 naturally triggered deep persistent slab occurred sometime in the last few days in the Pocaterra Ridge area. This avalanche had impressively wide propagation.

Snowpack Summary

Recent storm snow of approximately 25cm of settled snow remains dry on polar aspects and has seen little wind effect. However, solar aspects have now seen several generations of sun crust, and this recent snow was moist on the surface today on solar aspects.

Forecasters are tracking 3 main weak layers in the snowpack. First, a buried sun crust on solar aspects, 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 of facets buried 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

Wednesday should be a beautiful day with lots of sun, temps near +1C and freezing levels climbing to 2200m. Winds will be light from a variety of directions. No new snowfall is 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.
If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
Rocks will heat up with daytime warming and may become trigger points for loose wet avalanches
Avoid exposure to overhead avalanche terrain as temperatures increase.

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.

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.