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Avalanche Forecast

Archived

Jan 30th, 2017–Jan 31st, 2017

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

Regions

Little Yoho.

Ice climbers: be wary of recent loading that may not be evident at the valley bottom levels. Several events over the weekend originating at upper elevations affected the climbs at lower levels.

Weather Forecast

The jet stream that has been directly over our heads for the last few days will shift further south tonight. Cold northern air will return with north winds at upper elevations and plunging temperatures pushing away some remaining cloud and moisture. Clear, Calm and Cold by Wednesday night. This state of affairs looks to last until Friday.

Snowpack Summary

In many areas, a generally weak snowpack exists below 2000-2200m . At 2000m, there is generally 140 cm of snow, with the Jan 17 surface hoar layer down 30cm producing sudden planar test results. In the mid-pack, the Dec facets are 20cm thick, and near the ground some weak facets sit just below on an old ice crust.

Avalanche Summary

Strong to Extreme South and West winds have produced an avalanche cycle over the weekend that continued today. Sunday, natural avalanches could originating higher on Mts Stephen, Dennis and Field spilled over ice climbs at the valley bottom level. Fresh windslabs as well as avalanches involving deeper layers have been observed in the BYK region.

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.