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Avalanche Forecast

Archived

Dec 20th, 2013–Dec 21st, 2013

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

Little Yoho.

Even though the cool temps have tightened the snowpack, the potential to trigger full depth avalanches remains due to the weak base that will be a problem for some time to come. JBW

Weather Forecast

Cool northwesterly flow with some weak disturbances will continue for the next few days bring little snowfall but cold breezy conditions. Temps warm slightly by Sunday.

Snowpack Summary

Some moderate wind transport is adding to the slabs at treeline and above. This will increase the propagation potential across the start zone features. The weak base with depth hoar and the October melt freeze crust will mean any avalanche will involve the entire snowpack.

Avalanche Summary

No new avalanches were observed today, but we suspect a few more slabs pulling out on steep lee features with the additional loading. Avalanches to size three both natural and explosive triggered have occurred over the last few days some running full path.

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.