Archived

Avalanche Forecast

Jan 21st, 2016–Jan 22nd, 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

1: Low

The avalanche danger rating below treeline will be low

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

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.

Pay close attention to new snow amounts and whether or not the surface snow is loose or cohesive. Tricky conditions are likely if a cohesive slab forms.

Confidence

Low - Due to the number of field observations

Weather Forecast

Friday: Cloudy with up to 5 cm of new snow. The freezing level is at valley bottom and winds are moderate from the SW. Saturday: Mainly cloudy with sunny breaks and a chance of flurries. The freezing level is at valley bottom and winds ease to light. Sunday: Mainly cloudy with a chance of flurries. The freezing level is at valley bottom and winds are moderate from the southeast.

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

An additional 5-10 cm of snow with moderate or strong southeast winds may be enough to form fresh, reactive wind slabs in lee features. In some places this could also activate buried surface hoar in the upper snowpack, generally found between 30 and 60 cm deep. Stay tuned to signs of instability like recent avalanches, whumpfing, and shooting cracks. 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 wind slabs in exposed lee and cross-loaded terrain.

Use ridges or ribs to avoid pockets of wind loaded snow. >Watch for signs of the development of a more widespread storm slab problem, especially in the north of the region. >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 - 3

Persistent Slabs

New snow, wind, and mild temperatures may have helped develop a cohesive slab, which overlies a variety of buried persistent weaknesses. It may be easy for riders to trigger this slab (where it exists), even from low angle terrain.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 3