Archived

Avalanche Forecast

Jan 19th, 2013–Jan 20th, 2013

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Northwest Inland.

Confidence

Fair - Due to limited field observations

Weather Forecast

The stationary ridge of high pressure is expected to bring continued dry conditions to the region until Tuesday at which point the ridge moves east allowing light snowfall to affect westerly slopes. Alpine temperatures are forecast to be about 0.0` for Sunday and Monday, and then dropping on Tuesday. Winds should remain light to moderate from the southwest.

Avalanche Summary

A size 2 windslab avalanche was remotely triggered by a skier on Friday in the north of the region. It was triggered from 20m away on an east aspect at 1550m and ran 150m

Snowpack Summary

A melt freeze crust most likely exists on lower elevation slopes that were previously rain-soaked. Light to locally moderate amounts of recent snow and strong to extreme winds at higher elevations have formed hard windslabs in the lee of terrain breaks and ridges.A surface hoar layer that was buried at the end of December is now down 60-80 cm, and was reactive in some areas with recent warming but is most likely gaining strength.An otherwise strong mid-pack overlies a weak base layer of facets/depth hoar and the remnants of a crust.

Avalanche Problems

Wind Slabs

Strong to extreme westerly winds have created windslabs on lee terrain. With higher than normal wind values, watch for loading lower on the slope and in other unsuspecting locations.

Be aware of the potential for wide propagations due to the presence of hard windslabs.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Persistent Slabs

A layer of surface hoar buried at the end of December may still be reactive. Watch for triggering in sheltered, unsupported terrain.

Make observations and assess conditions continually as you travel.>Conditions have improved, but be mindful that persistent instabilities are still present.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 4

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 thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 5