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Archived

Avalanche Forecast

Jan 25th, 2017–Jan 26th, 2017
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
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
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high

Regions: Northwest Coastal.

A new Pacific storm system will start to brush up against the Northwest coast overnight. Avalanche danger will trend to HIGH by the weekend.

Confidence

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

Weather Forecast

A new Pacific storm system will start to brush up against the Northwest coast overnight. This series of low pressure systems will be deflected to the North by a strong ridge of High pressure over most of the province. Precipitation amounts are expected to be heaviest along the coast and near Kitimat and Stewart. Overnight: 5-10 cm, moderate southwest winds, freezing level 600 metres. Thursday: 10-25 cm with strong southwest winds, freezing level rising to 1000 metres. Friday: 20-40 cm with extreme southwest winds, freezing level rising to 1300 metres. Saturday: 25-50 cm with extreme southwest winds, freezing level rising to 1500 metres.

Avalanche Summary

One report on Wednesday of a skier triggered wind slab size 1.0 on a convex roll at 1500 metres that was about 25cm deep. Expect avalanche size and frequency to increase as the forecast storm moves into the region.

Snowpack Summary

There is 5-10 cm of new snow above the latest buried surface hoar layer from January 23rd that has been found up to size 10 mm at treeline and below. This surface hoar layer may be associated with a crust below 1100 metres. There continues to be several other surface hoar layers of concern from early January and Christmas. Some reports show these persistent weak layers to be rounding and bonding, however we are still getting some reports of sudden planar releases in snowpack tests with hard forces applied. I suspect the forecast heavy precipitation over the next few days will be a good test for these older buried weak layers.

Avalanche Problems

Storm Slabs

Storm slabs are expected to develop with forecast new snow and wind. Avalanche size and frequency will increase with each pulse of precipitation, increasing winds, and rising freezing levels.
If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Minimize exposure during periods of heavy loading from new snow, wind.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Persistent Slabs

It may still be possible to trigger avalanches on buried weak layers (Dec 25, Jan 5th, Jan 12th surface hoar) ...or have a smaller avalanche 'step down' and trigger one of these layers.
Assess start zones carefully and use safe travel techniques.Carefully evaluate terrain features by digging and testing on adjacent, safe slopes. Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3