Avalanche Forecast

Issued: Jan 31st, 2012 9:57AM

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

Avalanche Canada jlammers, Avalanche Canada

Summary

Confidence

Fair - Freezing levels are uncertain on Friday

Weather Forecast

Wednesday: 5-10cm of snow easing in the afternoon / moderate southwest winds / freezing level at 1100mThursday: clear / light northwest winds / freezing level at 900m rising in the afternoonFriday: clear skies with a significant warming trend / light and variable winds

Avalanche Summary

Numerous fresh windslab avalanches (size 1.5-2) were observed in the region on Monday in response to Sunday night's warming, moderate winds and continued snowfall. Explosives-controlled avalanches to size 3 were reported in the Kootenay Pass area. It should be said that most recent snowfall amounts were greatest in this area.More deep activity was reported from the Bonnington Range on Saturday where a size 2.5 and a size 3 avalanche were reported to have released on the mid-December surface hoar/facet layer.

Snowpack Summary

Warmer temperatures, moderate southwest winds and moderate snowfall on Sunday night has added to an ongoing wind slab issue creating cohesive and reactive wind slabs at treeline and in the alpine. In some parts of the region the underlying storm snow from last week is sitting on 1 or 2 freezing rain crusts that developed last Tuesday morning. Reactivity on the crust (which sits about 45cm below the surface in most wind-neutral areas) is possible with a large trigger. A few operators are also talking about a surface hoar layer that was buried on January 14th. Its reactivity has been described as "stubborn", but it has potential to size 3. A layer of concern deeper in the snowpack is the surface hoar/facet layer from mid-December. This layer has become less of a concern in the vast majority of locations. In the Bonnington Range, however, it is still on the radar of backcountry travelers as the layer is still reactive and is producing avalanches to size 3 in isolated features. This lingering layer of concern reflects the variability of the snowpack within the region.Snowpack depths in the region are around 230 cm at treeline. Looking forward, a significant warming trend and clear skies are forecast for late Thursday/Friday. Expect increased avalanche activity with this trend.

Problems

Wind Slabs

An icon showing Wind Slabs
Windslabs have set up in the lee of exposed features at treeline and in the alpine.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Storm Slabs

An icon showing Storm Slabs
Recent snowfall has added to the current storm slab problem. Watch for storm slabs on steeper, unsupported features

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 4

Cornices

An icon showing Cornices
Recent wind and snowfall has created sensitive new cornices at ridge top. Cornices can also be trigger for an avalanche on the slope below.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 5

Valid until: Feb 1st, 2012 8:00AM