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Avalanche Forecast

Archived

Nov 28th, 2020–Nov 29th, 2020

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

Regions

Little Yoho.

Strong to extreme winds have and will continue to keep the alpine hazard elevated for the next few days, as uncertainty surrounds the extent and sensitivity of newly formed wind slabs.

Weather Forecast

A mix of sun and cloud for Sunday as the winds are forecasted to increase throughout the day, 30-80km/hr at ridge top from the South West. Temperatures will range from -2 to -7. Monday could see another 2 - 5cm of snow, strong to extreme winds and a slight cooling trend.

Snowpack Summary

10cm of recent snow and strong Westerly winds suspected to be building wind slab in the alpine down to tree line. The Nov 5 facet/crust combo is down 50-80 cm and producing variable test results, but 'sudden' in fracture character. This crust extends up to 2500 m on N aspects and higher on solar aspects. Snow depths at treeline are 70-130 cm.

Avalanche Summary

Evidence of natural avalanche activity within the past 36hrs up to size 2 (mainly sz 1-1.5) observed and reported throughout the forecast region consisting of cornice failures, wind slabs and loose dry sluffing.

Confidence

Problems

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.

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.