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Avalanche Forecast

Archived

Feb 17th, 2023–Feb 18th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

North Rockies, Kakwa, McGregor, Pine Pass, Tumbler.

More snow, more wind. There is plenty of snow available for transport and variable winds in the forecast building touchy storm slabs and wind slabs. Conservative terrain choices are your best bet for the weekend.

Confidence

Moderate

Avalanche Summary

Several loose dry during the storm on Thursday. Touchy storm slabs up to size 1 as the storm amounts accumulated through the day

Looking forward, storm slabs will be reactive to human triggering and touchy at upper elevations where the new snow is being redistributed by variable winds.

The lower snowpack is slowly gaining strength, new snow and wind-driven snow, forming storm and wind slabs triggered by large loads like a cornice or machine may step down to these deeper weak layers. Continue to manage this problem by avoiding terrain that is steep, rocky, and shallow.

Snowpack Summary

Variable snowfall amounts across the region with Pine Pass, Core Lodge riding area, and the southwest receiving the highest amounts.

New snow and moderate to strong southwest winds have developed wind slabs at all elevations. These new wind slabs are developing over various surfaces of stiff old wind slabs in open terrain, soft snow in sheltered locations, and a melt-freeze crust below 1200 m and on steep south aspects. Cornices are becoming overhanging and reactive, and new snow and wind will further develop their growth.

The mid-pack is gaining strength and consists of rounding facets and melt-freeze crusts that are starting to degrade. A spotty surface hoar layer buried around January 4th can still be found between 60 to 80 cm. Avalanche activity has not been reported on this layer recently but it is still showing up in snowpack tests.

Near the base of the snowpack, a persistent weak layer composed of large and weak facets formed in November is strengthening slowly. This layer is most likely to be triggered in thin, rocky alpine and upper treeline terrain.

Weather Summary

Friday night

Cloudy with flurries, increasing snowfall overnight accumulation 15 to 20 cm, 30 to 40 km/h southwest winds switching to the northwest, treeline temperatures -10 °C.

Saturday

Cloudy with flurries easing in the afternoon, then picking up again overnight, highest amounts in the southwest of the region, accumulation 5 to 10 cm, 30 to 40 km/h northwest winds, treeline temperatures -10 °C.

Sunday

Cloudy with snowfall, accumulations of 10 to 15 cm, west winds 40 to 50 km/h, treeline temperatures -10 °C.

Monday

Mix sun and clouds, trace accumulations, 5 to 10 km/h winds, treeline temperatures -10 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid exposure to slopes that have cornices overhead.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.