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Avalanche Forecast

Archived

Jan 20th, 2013–Jan 21st, 2013

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

Regions

Little Yoho.

Climbers, skiers and boarders should be aware of hard wind-slabs in the alpine. Ski conditions are extremely variable. Expect better travel West of the continental divide.

Weather Forecast

Very little change is expected over the next few days. However, a small system may be gracious enough to deposit a few centimeters of snow late on Wednesday. This will not be enough of an input to change the danger rating.

Snowpack Summary

The strong winds from the last few days have created wind slabs in lee areas in the alpine. In some areas these wind slabs will be very hard. Otherwise the storm snow from last week has settled to approximately 25cm and sits on top of the Jan 6 interface, a combination of surface hoar and facets.

Avalanche Summary

No avalanches were observed or reported today. However, yesterday, a recreational party triggered a size 2, hard wind slab avalanche on Narao Shoulder, in Yoho National Park around tree line.

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.

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.