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Avalanche Forecast

Archived

Jan 13th, 2020–Jan 14th, 2020

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.
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.

Both superficial and basal problems exist in the snowpack right now and both can be expected to persist for some time. Conservative terrain selection, careful snowpack evaluation and cautious group management is essential for safe travel.

Weather Forecast

The Polar air continues to push from the prairies over the divide. Mixing with pacific air is creating thin cloud and very light snowfall. Lack of sunshine, combined with brisk winds, increasing Tuesday through Wednesday, will make the cold hard to deal with although the possibility of inversion may hold for Tuesday.

Snowpack Summary

30-50 cm of snow since Dec 31 sits over a variety of surfaces including facets, surface hoar and sun crust. Stability tests throughout the region show 'sudden planar' results on this interface. Reactive wind slabs exist in alpine and some tree line locations. In most areas there is a settled mid-pack over top of weaker basal layers.

Avalanche Summary

Parks Canada responded to a size 2.5 skier triggered avalanche on the South flanks of Mt. Hector Friday. This avalanche failed to the ground in the upper start zone and track.

Several naturals sz 2-3 were observed Thursday throughout the forecast region, some of which failed at the ground within the deep persistent layer.

Confidence

Due to the number of field observations

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.

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.