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Avalanche Forecast

Archived

Dec 27th, 2019–Dec 28th, 2019

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

Regions

Little Yoho.

Though natural avalanche activity has tapered off, human triggering remains likely. Choose less committing terrain and avoid large overhead hazard.

There have been a few close calls already this week.

Weather Forecast

Slightly warmer temperatures for the weekend with a slight inversion on Saturday morning. Expect an alpine high of -8 for Saturday and -4 for Sunday with moderate winds from the West. Skies will remain cloudy with no significant snow accumulations in the forecast.

Snowpack Summary

Surface hoar growth up to 5mm observed below tree line. Moderate SW winds are redistributing the 30-60cm of recent storm snow and forming wind slab on lee aspects. Below the new snow the snowpack structure is generally weak  consisting of facets and depth hoar and a Nov crust up to 2500m.

Avalanche Summary

A couple of windslab avalanches in the past 24 hours on alpine Northerly aspects. On Wednesday, explosive avalanche control at Sunshine ski area produced a sz 2 deep persistent slab. Recent reports of skier triggered avalanches within the region and reports of whumphing on the deep persistent layer continue today.

Confidence

Problems

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.

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.