Avalanche Forecast

Issued: Dec 17th, 2018 4:07PM

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

brian webster, Parks Canada

Banff Yoho Kootenay.

Additional forecasted snow on an already over-loaded snowpack will keep the avalanche danger elevated. Conservative route choices are essential.

Summary

Weather Forecast

Two significant frontal systems are lined up to move inland over the next three days. 25-40 cm of additional new snow is expected along the divide by end of day on Thursday. This snow will be accompanied by moderate to strong SW winds. Freezing levels remain at valley bottom.

Snowpack Summary

40 - 60 cm of recent snow overrides a weak interface (Dec 10 layer) consisting of facets and surface hoar. Fresh windslabs can be expected on lee (north and east) aspects. The lower snowpack is weak and facetted. Any avalanches initiated in the storm snow have potential to step down to this lower layer.

Avalanche Summary

Numerous natural and skier (or explosive) triggered avalanches up to 2.5 have been reported over the past few days. Avalanches may run further down slope than expected, so be cautious of overhead hazard.

Confidence

Problems

Storm Slabs

Up to 50cm of recent snow with additional storm snow expected will have created storm slabs and wind slabs at all elevations. These slabs will be reactive to skier triggering. Ice climbers pay attention to overhead hazard.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

The mid and lower portions of the snowpack are weak and are now overloaded with critical levels of snow. We expect avalanches to step down to this deeper layer.

Good day to make conservative terrain choices.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1.5 - 3

Valid until: Dec 18th, 2018 4:00PM