Avalanche Forecast

Issued: Dec 5th, 2014 4:18PM

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

patrick jerome, Parks Canada

Banff Yoho Kootenay.

Watch the temperatures on Saturday as freezing levels are expected to rise accompanied by light winds and light snow. Human triggered avalanches likelihood will rise as the snowpack has poor structure and is in a fragile state awaiting a trigger. PJ

Summary

Weather Forecast

Westerly flow will bring light snowfall amounts and light winds for the next few days but the main criteria this weekend will be warming temperature & rising freezing levels exceeding 1800 meters by Saturday afternoon. This will be one of the most significant weather criteria and needs to be monitored closely.

Snowpack Summary

The storm snow from last week's storm is a soft slab in sheltered locations and wind scoured and hard wind slab in open terrain at tree line and above. The lower half of the snowpack is complex and poorly structured, comprised of the facets (Nov 24th) at the interface of the recent storm snow and a series of thin crusts (Nov 6th) and depth hoar.

Avalanche Summary

There has not been a great deal of natural activity observed however explosive results were reported from around the ski areas and produced slab avalanches up to size 2.5 with the slab failing on the basal facets and crusts right on the ground. These kinds avalanches are a dirty & rough ride through scree, rocks and trees & are human trigger able.

Confidence

Freezing levels are uncertain on Saturday

Problems

Deep Persistent Slabs

The primary problem in the snowpack is the interface between the recent storm snow and the November 6th and 24th facet/crust interfaces. This is the problem responsible for the majority of the avalanches in the past week. Watch for remote triggering.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 3

Wind Slabs

Although cold temperatures have reduced the tension in many wind slabs there are places that have been ravaged by winds from many directions, especially in the alpine. Watch for pockets of hard slab near ridge tops and cross loaded features.

Be careful with wind loaded pockets while approaching and climbing ice routes.Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 2

Valid until: Dec 6th, 2014 4:00PM