Avalanche Forecast

Issued: Jan 9th, 2012 9:48AM

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

Avalanche Canada jfloyer, Avalanche Canada

Summary

Confidence

Good - -1

Weather Forecast

Light precipitation is expected for Tuesday with treeline temperatures around -8C and moderate southwesterly winds. For Wednesday, a ridge of high pressure sets up over this region, bringing dry, cold, clear weather. Treeline temperatures will drop to around -15C. Winds will be moderate to strong from the north. On Thursday, clouds will start to build ahead of a relatively weak frontal system, winds will become northwesterly and freezing levels will rise to around 1500 m.

Avalanche Summary

A sled-triggered size 3 slab avalanche was reported from the Flathead/ Lodgepole area on Saturday. The slide was 75cm deep and 100m wide and occurred on a northeast aspect at the 2100m elevation.Size 1.5 loose snow avalanches were reported in the Elkford area on Saturday.Please visit our incident report database (under bulletins) on our website for more details.

Snowpack Summary

The average HS (height of snow) in the Crowsnest North is 120cms and the Crowsnest South has 150cms. As we move further West into the Elk Valley North the HS is an average of 130cms. The Elk Valley South sits at 170cms.In the Flathead the avg. HS is 170cms. All snow depths indicated are at the 2000m elevation.In the alpine and exposed slopes at treeline windward aspects have been stripped of snow by strong winds over the past week, and lee slopes have widespread stiff wind slabs. Over the past few days, dribs and drabs of new snow has added to an overriding unconsolidated soft slab.In the mid pack, weak buried surface hoar layers can be found on North-NE slopes at treeline and below down approx. 30-55cms. The surface hoar may co-exist with facets that are result of the early December dry spell. This interface is still reactive and has produced numerous natural avalanches over the past week.At the bottom of the snowpack a variable facet/ crust/ facet sandwich is located with depth hoar up to size 5mm below the crust, and facets size 2mm above. There has been little in the way of recent activity on basal layers, but the nature of a release would be highly destructive.As a side note, the snow depths alone indicate that the region is highly variable in terms of snowpack structure. You should anticipate that layering and reactivity of weaknesses will also be variable throughout the region.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs can be found on lee and cross-loaded aspects at treeline and in the alpine. Cornices have been an issue with recent warm weather.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
A cohesive slab sits over a touchy surface hoar weakness buried in mid-December. Slides are still occurring on this layer. Avalanches on this layer will be large, destructive and more difficult to predict.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 6

Valid until: Jan 11th, 2012 8:00AM