Avalanche Forecast

Issued: Feb 11th, 2017 4:00PM

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

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

Human triggered avalanches will be likely on Sunday, and the possibility of very large natural avalanches remains possible. Stay on conservative terrain and avoid overhead exposure while the snowpack adjusts to the new load.

Summary

Weather Forecast

Continued moderate to strong westerly winds for Sunday, only trace amounts of snow, and temperatures in the -10 range at treeline. We will see a slow rising of the temperatures over the next 5 days, with valley temperatures well above freezing, and alpine temperatures approaching 0C.

Snowpack Summary

30-60cm of new snow in the past 10 days with extreme winds from the SW have created new snow slabs over a fundamentally weak snowpack comprised mostly of facets, buried wind layers, and depth hoar. We expect more avalanches on these weak facet layers over the next while as the snowpack adjusts to the load.

Avalanche Summary

Many natural, skier, and explosive triggered avalanches were observed and reported throughout the forecast region up to size 3 in the last 48hrs. Most are occurring within the storm snow, 30-60cm deep, with some "step down" avalanches in the deeper weak layers of the snowpack. These have been on many aspects and all elevations.

Confidence

Problems

Wind Slabs

Expect drifted snow to be deeper than 100 cm in leeward areas on Sunday and very susceptible to human triggering over the next few days. Give avalanche terrain a wide berth as fracture lines may extend further that you expect.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

The new snow has created a touchy slab over the weak facets at all elevations, resulting in many avalanches that could potentially run full path, of which there have been numerous examples.

Be aware of the potential for wide propagations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Loose Dry

Wind loading has resulted in numerous loose dry avalanches over the last 48 hours out of steep cliffs and gullies. This problem will remain Sunday as wind speeds stay elevated.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 12th, 2017 4:00PM