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Avalanche Forecast

Archived

Apr 10th, 2023–Apr 11th, 2023

Alpine
Natural and human triggered avalanches likely.
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 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

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

A significant storm on Monday/Tuesday will have added additional load to the snowpack (snow above 2000m and rain below). It will take some time for the snowpack to adjust to this load. Conservative terrain choices are in order.

Confidence

Moderate

Avalanche Summary

Road patrol to Kootenay Park showed numerous loose wet avalanches (below 1900m) up to size 2 running to middle of the runouts. Ski hills reported ski-cutting storm snow avalanches out of steeper terrain.

Snowpack Summary

Up to 20 cm of storm snow in the alpine (end of day Monday) overlies previous windslabs and suncrusts with rain saturated snow below 1800m. Storm slabs can be expected in the alpine and tree-line areas.

Several buried crusts can be found in the top 50-60 cm on solar aspects. The bottom of the snowpack remains facetted and weak.

Weather Summary

Monday Night: Freezing levels will reach valley bottoms. 5-10 cm of snow expected above tree-line.

Tuesday: Freezing Levels around 14-1600m. 10-15 cm of snow above 2000m. Winds will be 20-40km/h from W/SW.

Wednesday: Cloudy skies with light flurries that will be convective in nature. Freezing Levels 14-1600m.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.