Avalanche Forecast

Archived

Jan 23rd, 2024–Jan 24th, 2024

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 possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

The snowpack is becoming increasingly complex.

Incremental inputs of snow with wind and mild temperatures are prompting the development of slab properties in the upper snowpack.

"Arctic Facets" from the cold snap fall apart easily in steep terrain and a layer of surface hoar or sun crust buried early in January lingers in some areas

Confidence

Moderate

Avalanche Summary

Avalanche control Monday on Mt Whymper produced several avalanches to size 2.5 starting at 2700 m and running to the top of the runout zones. These were 20-40 cm wind slabs that ran further than expected in the loose surface snow. Control in the Simpson area produced several size 2 avalanches at 2200m, failing 40 cm down on surface hoar and propagating 50-70 meters wide.

Snowpack Summary

Two weak layers each produce test results in some locations across the region as slab formation is taking place in the upper snowpack. Facets are buried down15cm and a layer of surface hoar sits at about 40cm deep.

The midpack offers some strength and features two crusts that persist as high as 2350m.

The lower part of the snowpack has weak facets and depth hoar and widespread whumphing has been observed in many locations over the last week.

Monday's snow profile from Simpson.

Weather Summary

We should expect flurries throughout the day on Wednesday with strong to extreme winds at higher elevations. Look for temperatures to cool slightly after warmer weather pushed in on Tuesday. Expect freezing levels to return to valley bottom.

Terrain and Travel Advice

Avoid areas where the snow feels stiff and/or slabby.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Use appropriate sluff management techniques.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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.