Avalanche Forecast

Issued: Nov 28th, 2017 4:00PM

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

jonas hoke, Parks Canada

Jasper.

A complex series of avalanche problems exists, conservative decision making and route selection is necessary.

Summary

Weather Forecast

A weak ridge builds Wednesday giving a break in the wind and snowfall.Wednesday: Clear periods and isolated flurries. Trace-5cm of snow. Alpine Low -10 C, High -9 C. Ridge wind moderate gusting strong from the West. Freezing level at valley bottom.Later in the week a Westerly flow will give alternating waves of flurries and clear periods.

Snowpack Summary

Wind slabs continue to build in exposed lee features.Â Storm slabs formed with 40cm of snowfall over the weekend.Â These problems sit on a recently developed rain crust 30-60cm deep. A persistent slab up to 200cm thick sits on the Halloween Crust, low in the snowpack. This crust can be found up to 2,700m depending on location.

Avalanche Summary

No avalanche patrol today. Explosive control work on highway 93 yesterday produced avalanches up to size 2.5. These avalanches released as newly formed wind slabs up to 70cm thick as well as one persistent slab up to 150cm thick releasing on the Halloween crust.

Confidence

Forecast snowfall amounts are uncertain

Problems

Wind Slabs

Sensitive wind slabs building quickly at ridge tops and if triggered, has the potential to step down to the deeper instability.

Avoid freshly wind loaded features.Avoid avalanche terrain during periods of heavy loading from new snow and wind.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Storm Slabs

Storms slabs continue to be an issues as the recent snow settles. Cooler temperatures over the next few days will help heal this problem.

If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

This is a complex problem which is hard to assess and predict. Give yourself a wide margin and make conservative terrain choices. Below treeline this layer is only a concern if you are in a run out zone of a large avalanche path.

Be aware of the potential for wide propagations.Be wary of slopes that did not previously avalanche.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Nov 29th, 2017 4:00PM