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Avalanche Forecast

Archived

Jan 17th, 2015–Jan 18th, 2015

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

20-30cm of new snow is forecast to fall in the Little Yoho region by early Monday morning accompanied by strong W winds. We will see the hazard rise throughout Sunday and expect to see the peak avalanche activity late Sunday night and into Monday.

Weather Forecast

A storm is forecast to arrive by mid day on Sunday bringing 20-30cm of new snow and very strong West winds at ridge top. The winds ease off a little on Monday and switch to the NW with a few more cm`s of snow forecast for Monday and Tuesday. Treeline temperatures remain between -4 and -10`C.

Snowpack Summary

The main concern in the snowpack is the Dec 18 surface hoar layer down 40-50 cm. This layer is very prominent and is producing moderate test results and lots of whumphing. 10cm of new snow in the last 48hrs combined with the 20 - 30 expected on Sunday will likely reactivate this layer.

Avalanche Summary

No new avalanches observed or reported in last 72 hours.

Confidence

Timing of incoming weather systems is uncertain on Sunday

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.