Avalanche Forecast

Issued: Feb 10th, 2020 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is low. Known problems include Wind Slabs and Deep Persistent Slabs.

Parks Canada aaron beardmore, Parks Canada

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Little Yoho.

Uncertainty remains around deep persistent slab avalanches and their random occurrences. If they do occur, there is the possibility that they can run to valley floor.

Summary

Weather Forecast

Seasonal temperatures are expected for the next few days. Snow will start late tonight and roughly 10cm will accumulate by end of day Tuesday. Alongside the incoming snow will be strong wind from SW.

Snowpack Summary

Up to 20 cm of snow in the past several days. Recent periods of strong wind have created fresh wind slabs at treeline and in the alpine. In many areas a dense mid pack sits over the basal weak layers of facets and depth hoar. Deep snowpack areas (>150 cm) have a denser base. A buried rain crust from February 1st is present up to 1850 m.

Avalanche Summary

A large deep persistent slab avalanche (size 3.5) was observed on the East face of Mt. Lefroy than released on glacier ice today. Additionally, a size 1.5 windslab was observed on Protection Mountain on a SW aspect in the alpine.

Confidence

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

Problems

Wind Slabs

An icon showing Wind Slabs

Strong SW winds and new snow is forecasted for Tuesday. When this materializes expect new wind slabs in lee areas. These could be triggered by skiers or climbers. Travel where you can avoid wind slabs until they have a chance to bond.

  • Use caution in lee areas. Recent wind loading has created wind slabs.
  • If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

High consequence avalanches on the facets and depth hoar at the base of the snowpack remain possible. Large triggers such as cornices and wind slabs, or human triggering in thin snowpack areas are most likely to result in avalanches on this layer.

  • Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.
  • Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Feb 11th, 2020 4:00PM

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