Avalanche Forecast

Issued: Dec 23rd, 2016 4:26PM

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

Parks Canada stephen holeczi, Parks Canada

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Banff Yoho Kootenay.

We now have a typical rockies snowpack with wind slabs sitting over a variety of very weak layers. It will be tricky to assess this persistent slab problem. Time to step way back and limit your exposure to avalanche terrain at treeline and above. SH

Summary

Weather Forecast

Light winds with a SE flow for the weekend and some light snow in Eastern regions.  Alpine temperatures will be in the -14C range.  A Westerly flow reasserts itself on Monday with some light precipitation and moderate winds. 

Snowpack Summary

An average of 10-30cm sits over the very weak Dec.19th facets. Wind slabs up to 60cm have been observed over this same layer in alpine areas. The windslab/facet interface was touchy in avalanche control work over the last 2 days and will persist for some time. The Nov crust is 30-80cm and as yet there are limited observations of it being reactive.

Avalanche Summary

Explosive control Wed/Thurs resulted in avalanches up to size 2.5-3 where wind effect was prevalent. The slabs failed on the persistent Dec.19th facets. Ski hills triggered a couple of size 2's with bombs, initiating on the Nov 12 crust on solar aspects with a thin snowpack where the crust is more pronounced. Not many naturals reported or seen.

Confidence

Due to the number and quality of field observations

Problems

Persistent Slabs

An icon showing Persistent Slabs
New snow and strong winds have created  wind-slabs on exposed slopes that can be easily triggered. These slabs sit over a very faceted snowpack creating a weak interface that will last for some time. 
Use caution in lee areas. Recent wind loading have created wind slabs.Be careful with wind loaded pockets while approaching and climbing ice routes.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Dec 24th, 2016 4:00PM

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