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Avalanche Forecast

Jan 22nd, 2012–Jan 23rd, 2012
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
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.

Confidence

Fair - Freezing levels are uncertain on Tuesday

Weather Forecast

Light flurries on Sunday are expected to become moderate snowfall overnight into Monday morning, bringing 10-15 cm to the mountains near Terrace, and 5-10 cm more inland near Smithers. Moderate south winds on Sunday night are forecast to swing to the southeast by Monday morning and then shift to southwest and build to about 35 km/hr at ridgetops by Monday afternoon. This is a relatively fast moving low pressure between two week ridges of high pressure. The next big event is forecast for Tuesday morning, when freezing levels are expected to begin to rise and heavy precipitation combined with strong southwest winds will move into the region from the Pacific. Freezing levels are expected to briefly rise as high as 1500 metres by Tuesday afternoon. Temperatures should cool and snow should continue on Wednesday.

Avalanche Summary

Reports of widespread whumpfing at treeline and above on hard windslabs. Skier accidental reported to size 2.0 from a south aspect on a convex roll in the backcountry near Shames on Saturday.

Snowpack Summary

The main concern is windslab. The old windslabs are on south through west aspects, and they are stiff and continue to be easily triggered. New windslabs are building on north through east aspects, making travel a bit tricky; limited options exist for avoiding both types of windslab. Change is coming on Monday night or Tuesday morning, when heavy snowfall and warmer temperatures may overload all of the current weakness. I have left in the paragraph from yesterday because the problems are slow to heal, and I believe they are still valid. The deep snowpack is considered to be well settled with no persistent layers of concern. There is now 30-40 cm of dry cold snow above windslabs that have developed due to strong NE outflow winds which have not bonded to the January 8th surface. These pockets of hard windslab can be triggered by light loads such as a single skier or rider. Some areas have developed surface hoar or surface facetting on sheltered slopes in the alpine and at treeline, that are now getting buried by new snow and shifting winds.

Avalanche Problems

Wind Slabs

Old stiff windslabs on south through west aspects are poorly bonded to the old surface and may be triggered by skiers and riders. New windslabs continue to develop on north through east aspects.

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

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 2 - 5

Storm Slabs

Forecast strong southerly winds combined with moderate precipitation may develop a storm slab. If temperatures remain cool the new snow may continue to be loose and dry causing widespread sluffing.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 5