Avalanche Forecast

Archived

Apr 12th, 2023–Apr 13th, 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 possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

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

The storm slab is still very sensitive to human triggering and the potential for this layer to step down to the deeper layers of the snowpack exists.

If the sun is shinning, be mindful of its power to create avalanches at this time of year.

Confidence

Moderate

Avalanche Summary

While the natural avalanche activity has tapered slightly, the cycle is still ongoing. Storm slabs, loose wet, cornice fall and deep persistent slabs have all been observed and/or reported in the last 24h up to size 3. Heli bombing today produced results up to size 3.5, some avalanches initiating as soon as the bomb hit the slope.

Snowpack Summary

Up to 35 cm thick storm slabs overlies previous windslabs on polar aspects and suncrusts on solar aspects, with rain saturated snow below 1800m. Solar slopes will have a new crust up to 1900m.

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

Thursday: Partially cloudy skies through the day and as much as 10cm's of snow from Wednesday evening through to the end of the day Thursday. There is a small chance of a thunderstorm Thursday afternoon as well. Winds will be light and freezing levels will be between 1600-1800m, with the alpine high between +2 and -3.

Friday: Cloudy skies with convective activity through the day on Friday. A chance of thunderstorms is mentioned in. Freezing levels will be higher, between 1700-2000m and the winds will increase into the moderate range.

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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.

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.