Avalanche Forecast

Issued: Jan 15th, 2013 9:43AM

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

jlammers, Avalanche Canada

Northwest Inland.

Snowfall amounts are highly uncertain for the forecast period. Danger ratings are based on forecast models which call for higher accumulations.

Summary

Confidence

Poor - Forecast snowfall amounts are uncertain for the entire period

Weather Forecast

Overnight and Wednesday: Light to moderate snowfall / Strong to extreme west winds / Freezing level climbing to 1000mThursday: Heavy snowfall / Strong to extreme west winds / Freezing level at 800mFriday: Light snowfall / Moderate west winds / Freezing level at 700m

Avalanche Summary

On Monday a size 2 windslab avalanche was skier-triggered in a chute above Crater Lake. The crown was about 30m wide with a maximum height of 80cm.

Snowpack Summary

A surface hoar layer that was buried at the end of December is now down 60-80 cm, and has become reactive in some areas with recent warming. There are also signs of recent intense northwest winds in the alpine and at treeline leaving scoured areas and hard windslabs on lee side of ridges and terrain breaks.Â A strong mid-pack overlies a weak base layer of facets/depth hoar and the remnants of a crust.

Problems

Wind Slabs

Strong westerly winds are forecast to create new windslabs on lee terrain. With higher than normal wind values, watch for loading lower on the slope and in other unsuspecting locations.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

New snow will add additional load to buried weak layers. Watch for triggering in steeper, unsupported terrain.

Be aware of the potential for large avalanches due to the presence of buried surface hoar.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Deep Persistent Slabs

A deeply buried facet/crust weakness exists near the base of the snowpack. This layer could be triggered by large loads such as a cornice collapse or from a thin-spot trigger point.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Jan 16th, 2013 2:00PM