Archived

Avalanche Forecast

Jan 20th, 2016–Jan 21st, 2016

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

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

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Northwest Inland.

Stay tuned to signs of instability like recent avalanches, whumpfing, and shooting cracks. If observed, back off to simple terrain with no overhead exposure.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Tonight and Thursday: 5-15 cm of snow. The freezing level is at valley bottom. Winds are strong from the Southwest. Friday: Cloudy with flurries. The freezing level is at valley bottom and winds are moderate from the SW. Saturday: Mainly cloudy with a chance of flurries. The freezing level is near valley bottom and winds ease to light.

Avalanche Summary

There is a new report of two skier controlled size 2 slab avalanches from the Ashman area on Tuesday. These failed on the Jan 5/Dec 26 surface hoar layers down 20-50 cm deep. On Monday, a small natural cornice release triggered a size 2.5 slab avalanche in the north of the region. Skiers also triggered a few slab avalanches size 1-2 in the north. All these avalanches released on the Jan 9 surface hoar layer down 30cm.

Snowpack Summary

The region has a mix of wind slabs and developing storm slabs. In higher snowpack areas in the northwest of the region, the storm slab has become reactive to human triggers. In most other areas the wind slabs are thin and stiff. Buried surface hoar is layered through the thin snowpack. Cool temperatures and limited loading have preserved these weak layers. The mid pack that was reported to be well settled may have now facetted in the shallower areas, and the deeper basal layers are almost certainly facetted and weak. We have not heard of any full depth releases on weak basal layers yet.

Avalanche Problems

Wind Slabs

Expect to find fresh pockets of wind slab in exposed lee and cross-loaded terrain. These may be extra touchy in place where buried surface hoar may be preserved.

Be cautious as you transition into wind affected terrain. >Watch for signs of the development of a more widespread storm slab problem, especially in the north of the region. >Use ridges or ribs to avoid pockets of wind loaded snow. >

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Persistent Slabs

Some areas could see enough new snow and wind to create a slab over the buried surface hoar layer, currently 20-40 cm deep. Stay tuned to changing conditions and head out with options.

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 4