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Archived

Avalanche Forecast

Jan 20th, 2018–Jan 21st, 2018
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
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
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
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Glacier.

Human triggering of sensitive weak layers is likely. Careful evaluation of the snowpack is required for safe travel.

Weather Forecast

Cloudy with sunny periods and isolated flurries bringing 2-5 cms. Alpine temperatures will be steady around -8 with freezing levels reaching 1100m. Winds in the alpine will be 25-35 from the Southwest.  Expect unsettled weather over the weekend and early next week.  Sunday looks like the stormiest day with strong winds and 10-20cms of snow forecast

Snowpack Summary

Around 35cm of new storm snow sits atop the January 16 surface hoar layer which is settling quickly and reactive in tests(video here). Strong South winds have redistributed the recent snow in the Alpine. The December 15 surface hoar is down 100cm and is highly visible in profiles. This layer is still producing sudden planar results in tests

Avalanche Summary

In the previous 48 hrs we experienced a natural avalanche cycle triggered by strong winds and snowfall. Forecasters observed size 2-3 avalanches in steep north facing alpine paths.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

Avalanche Problems

Storm Slabs

Previous strong Southerly winds combined with recent new snow has led to surface slab development. This buries the Jan 16 surface hoar layer which is widespread and found down 30cm. Slabs triggered over this weak layer could propagate far.
Use caution in alpine lees. Recent snowfall mixed with wind loading has created storm slabs.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1.5 - 2.5

Persistent Slabs

The January 4th surface hoar is down 60cm and the Dec 15th layer is down 100cm. After a month under the snow, this surface hoar remains widespread and well-preserved. These layers should not be overlooked and could be more sensitive in thin areas.
Dig down to find and test weak layers before committing to a line.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3.5