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Avalanche Forecast

Archived

Feb 3rd, 2017–Feb 4th, 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 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.

There is a lot of uncertainty with the weather, including snowfall amounts, over the weekend. If significant snowfall arrives expect to see an increase in avalanche activity on the persistent layers.

Weather Forecast

A low over the coast is spreading a stream of moisture to the Southern Rockies while competing polar air overlies our forecast area. The amount of snow that arrives depends on which of these two air masses is the strongest and where the boundary between them ends up varying between 10 and 30cm. Temps and winds will be equally difficult to predict.

Snowpack Summary

Strong winds last weekend created extensive wind effect TL and above. A generally weak snowpack exists below 2000m. At 2000m there is about 140 cm with the Jan 17 surface hoar layer down 30cm. In the mid-pack, the Dec facets are around 20cm thick. Weak facets can also be found at the base of the snowpack associated with an ice crust.

Avalanche Summary

There was a small avalanche cycle last weekend from strong winds. The activity has slowed significantly due to decreased winds and cooling temperatures. No avalanches reported Thursday or Friday.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Saturday

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.