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Avalanche Forecast

Archived

Mar 9th, 2014–Mar 10th, 2014

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

The natural cycle is slowing down but skier triggering of avalanches remains likely. Choose moderate terrain with minimal exposure to large paths, and watch for the effects of daytime heating as we move into more spring like weather. CJ

Weather Forecast

Alpine temperatures between -10'C and -3'C are forecast for the next several days, with a mix of sun and cloud, occasional light flurries, and light to moderate winds out of the West.

Snowpack Summary

85-100cm of storm snow has fallen in the Sunshine, Kootenay and Yoho areas, with 40-60cm around Lake Louise and Bow Summit since Mar 2nd. This storm snow has overloaded the Feb 10th layer of facets, surface hoar and sun crust, causing avalanches with wide propagations. Moderate SW winds have also created wind slabs in open areas above tree line.

Avalanche Summary

A widespread natural avalanche cycle to size 3 occurred on all elevations and aspects today. Much of this is occurring on the Feb 10th layer however we also observed storm slab releases and some deep releases to ground. The cooler temperatures over the next several days will slow down the natural cycle, but skier triggering will remain a concern.

Confidence

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.

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.

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.