Avalanche Forecast

Issued: Dec 28th, 2014 1:14PM

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

tim haggarty, Parks Canada

Waterton Lakes.

More snow has increased the likelihood and consequence of avalanche. Use conservative terrain selection and avoid complex terrain. Remember coverage has been poor below treeline and new snow may be barely hiding many hazards.

Summary

Weather Forecast

Arctic air has taken over the weather and is squeezing the last of the moisture out of the last system from the coast over the prairies as the temperatures drop. By Monday night things will become dry as temperatures hit bottom at around - 25. Winds will be out of the North for the period which generally means they will be on the divide.

Snowpack Summary

Another 10cm of new snow fell on the divide Saturday night with double this over the front ranges. The slab over the persistent weak layer consisting of Surface Hoar and Facets over a strong crust is now 80 to 100cm thick. The new snow is hiding windslabs built by strong west winds at alpine and treeline elevations.

Avalanche Summary

The new snow is hiding any evidence ofÂ recent avalanche activity however at least one large natural was seen between the storms on Friday.Â This slab failed just beneath the cornice above Forum lake, 100m wide and pulled several other slabs as it scoured down the steep alpine face.Â Reports of skier triggering continue in nearby areas.

Confidence

Due to the number of field observations

Problems

Persistent Slabs

The weak snow above the crust is now primed with a big enough slab for there to be serious consequences. In the alpine this problem will likely be limited to N and E aspects but at treeline it is widespread. Use extra care in open, sheltered terrain.

Dig down to find and test weak layers before committing to a line.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Wind Slabs

Remember that previous West Winds had a strong effect on the current distribution of snowpack: fragile cornices and buried windslabs will complicate the picture and limit terrain choice as travelers look to avoid the persistent slabs

The recent snow may now be hiding windslabs that were easily visible before the snow fell.Do not travel on slopes that are exposed to cornices overhead.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Loose Dry

The new snow will be very sensitive to skier traffic in steep terrain. Remember that there are some serious slabs lurking beneath the surface that could be triggered by these sluffs.

Sluffs may trigger deeper instabilities.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2

Valid until: Dec 29th, 2014 1:14PM