Avalanche Forecast

Issued: Feb 12th, 2015 4:00PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

Natural activity is tapering, but conditions are still prime for human triggering. Conservative terrain selection is a must as we transition out of a large avalanche cycle.

Summary

Weather Forecast

Continued warm temperatures with freezing levels around 2000m until Saturday AM. The winds have picked up from the west and are forecasted to be in the moderate to strong range at ridgetop until Saturday PM. A small bout of precipitation (5mm) on Friday overnight, but otherwise partly cloudy skies with a clearing trend Saturday AM.

Snowpack Summary

45-70 cm of storm snow overlies either a rain crust or facets from January 30th. This snow combined with warm temperatures has created storm and wind slabs overlying the Jan. 30th interface. The basal facet/depth hoar layers are still active in shallow snowpack areas. Little recovery overnight created isothermal conditions below 1800m today.

Avalanche Summary

Natural avalanche activity is tapering as the snowpack slowly adjusts to the new load. However, moderate to hard sudden collapse snowpack tests today in the Bow Summit area indicate skier triggering is still very possible.

Confidence

Problems

Storm Slabs

50 to 90 cm of storm snow exist on the January 30th interface which is a crust below 2000m and facets above. A poor bond exists at this interface and large avalanches have been observed running on this layer. Wide propagations are still possible.

If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

Recent winds have created wind slabs in the lee of alpine features.

Use caution in lee areas. Recent wind loading have created wind slabs.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 3

Deep Persistent Slabs

The base of the snowpack remains weak due to basal depth hoar/facets. Initiation of a wind slab or a storm slab may step down to trigger large avalanches in thin snowpack areas.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Feb 13th, 2015 4:00PM