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Archived

Avalanche Forecast

Jan 31st, 2018–Feb 1st, 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
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
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
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

Regions: Northwest Coastal.

The incoming weather will give little time for storm slabs to heal. Stick to supported slopes and watch for signs of unstable snow such as whumpfs and cracks.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

THURSDAY: Flurries with 5 cm accumulations / moderate southwest wind / alpine temperatures around -6 C.FRIDAY: 10-20 cm of snow / moderate to strong southwest wind / alpine temperatures around -3 C.SATURDAY: 15-30 cm of snow / moderate to strong west wind / alpine temperatures around -1 C.

Avalanche Summary

Preliminary reports of a few large avalanches suggest a widespread natural avalanche cycle occurred during Tuesday's storm.The most recent report of a persistent slab avalanche  was on Saturday, when a size 2 avalanche on a buried surface hoar layer was remotely triggered on a northeast aspect in the alpine. Tuesday's storm would have tested the various persistent weak layers in the region, but at the moment we don't have enough observations to know whether or not they layers were reactive during the storm.

Snowpack Summary

Westerly winds and ongoing flurries are likely building fresh wind slabs in exposed terrain. This sits above 50 cm of settling snow from Tuesday's storm, which is likely still reactive to human triggers.A weak layer buried in mid-January remains a concern and is now 60-100 cm deep. In most areas this layer is a crust, but it may also be surface hoar in sheltered areas at treeline and below. Prior to the storm, this layer produced sudden snowpack test results in the Shames area and avalanche activity at upper treeline and alpine elevations. Professionals have also been monitoring another two crust / surface hoar layer that were buried in mid-December and early January that are now 100-150 cm deep. These layers were most recently active in northern parts of the region near Bear Pass.

Avalanche Problems

Storm Slabs

50 cm of recent snow has formed fresh storm slabs. Slabs will be most reactive in wind-affected terrain at higher elevations.
Minimize exposure during periods of heavy loading from new snow and wind.Be cautious as you transition into wind affected terrain.Choose well supported terrain without convexities.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 2

Persistent Slabs

Several weak layers in the upper snowpack have the potential to produce large avalanches. Sheltered treeline areas with preserved surface hoar are the most suspect for human triggering.
Watch for signs of instability such as whumpfing, or cracking. Avoid shallow, or thick to thin snowpack areas where triggering a deeper layer is more likely.Be cautious on convex rolls at treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1.5 - 3