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Avalanche Forecast

Archived

Jan 27th, 2015–Jan 28th, 2015

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

Regions

Little Yoho.

A cooling trend should tighten up the snowpack below treeline. Pay attention to fresh  windslabs in the alpine.

Weather Forecast

A mix of sun and cloud expected for Wednesday and Thursday. A cooling trend is forecasted with overnight freezing levels at the valley floor and rising to 1400 meters during the day. Ridge top winds will be moderate from the west.

Snowpack Summary

Very strong westerly winds have seriously blasted the region. Wind pressed snow and wind slabs in lee terrain can be expected in the alpine. On Tuesday the snowpack was isothermal below treeline in many areas, but we expect this condition to improve with forecasted cooler temperatures on Wednesday.

Avalanche Summary

The warm temperatures created a widespread avalanche cycle on Sunday and Monday. Tuesday saw slightly cooler temperatures and less natural activity. Avalanches observed were restricted to isothermal avalanches in shallow snowpack areas below treeline.

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.