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Avalanche Forecast

Archived

Jan 20th, 2018–Jan 21st, 2018

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

Regions

Little Yoho.

There is still lots of uncertainty on how the surface hoar at treeline will react. Make conservative terrain choices at this elevation and take the time to look in the snowpack for this problem.

Weather Forecast

A few cm expected Sunday with increasing SW winds. Highs will be -5 to -8C at valley bottom and -12C at 3000m.

Snowpack Summary

Recent winds have developed windslabs on alpine and treeline lee slopes. In sheltered areas the upper snowpack has 20-30cm of soft slab over the Jan 6 surface hoar, and this layer has been reactive in test results. The Dec. 15 surface hoar layer is still a concern in the region, in many areas this layer is 50-80 cm down with a settled slab above.

Avalanche Summary

No new avalanche activity reported in this forecast region.

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.