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Avalanche Forecast

Archived

Nov 19th, 2021–Nov 20th, 2021

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

Jasper.

The Forecast team considers the likelihood of triggering is going down but the consequence is severe if anything is triggered. As Senior Forecaster Cory Boschman says "ski lightly and think conservatively".

Weather Forecast

Saturday will be cloudy and flurries, 4 cm of snow, -9 degrees and 20 km/h gusting to 60 km/h W to SW winds. Sunday will be similar to Saturday with less winds. The sun may poke out on Monday and no new snow is expected.

Snowpack Summary

Surface hoar is forming up to 4mm on the 60-80cm of storm snow that fell Nov 13-15th. The storm snow has settled into a persistent slab particularly where the wind has influence. A 2cm thick crust 80cm down is found up to 2500m or higher. Weak facets are below the crust resulting in sudden collapse test results. This should cue you to be cautious.

Avalanche Summary

Friday's team observed two size 2 persistent slab avalanches on windloaded features in the alpine and treeline. On Wednesday numerous avalanches up to size 3.5, generally from steep alpine features, were noted. They occurred during or at the end of the Nov 13-15th storm. One  800m wide avalanche was caused by explosives at tree-line on Tuesday.

Confidence

Wind effect is extremely variable on Saturday

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.