Avalanche Forecast

Issued: Dec 28th, 2016 3:00PM

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

Alberta Parks matt.mueller, Alberta Parks

The weak mid pack will take some time to stabilize. Fresh snow loading, either by wind or new snow, will tip the scales towards an avalanche cycle. Avoid large terrain while the snowpack adjusts.

Summary

Confidence

-

Weather Forecast

Snow beginning Thursday afternoon or evening bringing 10 cm. The winds will continue overnight tonight, but taper slightly as the incoming weather passes. Expect SW winds at 40km/hr in the alpine tomorrow. Temperatures will range from -8 at the road to -10 at ridge top.

Avalanche Summary

One slab was noticed today below a large alpine cliff face. Sz 2(estimated, debris pile was not seen), E asp, 2500m. From a distance it looked about 60cm deep and 100m wide. Likely ran on the Dec 18th facets.

Snowpack Summary

The steady winds that we've been experiencing lately are significantly changing our snowpack. Windslabs are the current problem at the forefront of our minds. We are starting to see them even below treeline, however they are of little concern as there is still very little snow at valley bottom. Open areas at treeline is where the slabs start to become a legitimate concern. At the moment, the slabs as a whole are up 40cm thick. This thick layer is actually made up a series of laminated slabs from various wind events. These slabs are sitting on a delicate layer of facets that were buried on Deb 18th. This facet layer is widespread and will likely last for weeks to come. Snow depth at treeline was 125cm today. The alpine has a similar condition in terms of windslabs and weak layers underneath. We are finding the Dec 18th facets alive and well in most areas. In thinner snowpack areas, these facets are more pronounced and have turned into depth hoar. The snow coverage is variable with dramatic transitions. It will go from gravel to a meter deep snowpack in only a few steps. Wind loaded areas will have a surprising amount of snow in them.

Problems

Wind Slabs

An icon showing Wind Slabs
These continued to grow today. Whumphing and cracking was observed as forecasters approached windloaded areas at treeline. Thin to thick snowpack areas should be treated with caution.
If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Avoid freshly wind loaded features.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Its thought that the windslabs are very likely to step down to this layer. Large avalanches are possible. Thin spots are now on our radar as trigger points for this layer. 
Use conservative route selection, choose moderate angled and supported terrain with low consequence.Pay attention to overhead hazards like cornices.Be aware of the potential for wide propagations.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

2 - 3

Valid until: Dec 29th, 2016 2:00PM

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