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Avalanche Forecast

Archived

Nov 27th, 2021–Nov 28th, 2021

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

Regions

Little Yoho.

Another big storm will increase the hazard on Sunday. Expect natural and skier triggered avalanche activity to occur as the storm arrives.

Weather Forecast

Another significant storm arrives Saturday night. Forecasts show 20 to 40 cm of incoming snow by the end of Sunday with strong SW-W winds and freezing levels rising to 2000 m. Lower elevations will likely see some rain fall during the storm.

Snowpack Summary

10-30 cm of storm snow sits over a layer of wind hammered snow in the alpine. In some locations this new snow is not bonding well to underlying hard surfaces. The Nov 15 crust is 30-50 cm down and present up to 2100 m. The Nov 5 crust/facet layer exists near the ground. Snowpack depths at tree-line average 80-110 cm.

Avalanche Summary

One skier triggered size 2.5 occurred in the Lipalian area near Lake Louise on Saturday and failed on the basel facets. Several ski controlled or explosive triggered wind slabs up to size 1.5 were also reported by the local ski areas. No natural avalanches were observed however visibility was limited.

Confidence

Intensity of incoming weather systems is uncertain

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 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.