Avalanche Forecast

Issued: Feb 7th, 2015 6:07PM

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

aaron beardmore, Parks Canada

Banff Yoho Kootenay.

Warm temperatures and an isothermal snowpack at low elevations is keeping the danger rating high. Avalanche control planned for tomorrow on Mt. Bosworth, Field and Stephen. No activities in these areas.

Summary

Weather Forecast

The intense precipitation is starting to taper off. Expect no more than 10cm of snow over the forecast region over the next couple of days with light west wind.

Snowpack Summary

45 - 70 cm of recent storm overlies a crust from January 30th. The recent heavy precipitation, wind and warmer temperatures have created storm slabs which will put an enormous amount of stress on the January 30th crust interface. The basal facets from Nov 6th could reemerge in step down events with this huge stress to the snowpack.

Avalanche Summary

Avalanche control on Mt. Whymper today produced avalanches up to size 2.5. Fracture line thickness varied between 20 and 60cm with average running distance about 250m. Also, evidence of a widespread cycle up to size 3 throughout the forecast region. Some avalanches running close to full path.

Confidence

Freezing levels are uncertain on Sunday

Problems

Storm Slabs

Storm slabs are the primary issue in the upper snowpack and failures will be occurring both within the colder low density and on the January 30th crust interface. This problem will be most prominent in the alpine and treeline bands on all aspects.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 3

Deep Persistent Slabs

The base of the snowpack remains weak due to basal depth hoar/facets. Additional snow load, or a storm slab failure may trigger large to very large avalanches in thin snowpack areas. There were additional avalanches triggered on these facets today.

Avoid lingering in runout zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Feb 8th, 2015 4:00PM