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Avalanche Forecast

Jan 6th, 2013–Jan 7th, 2013
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
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
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

Regions: Northwest Coastal.

If 20cm of snow or more is on the ground by noon on Monday, consider alpine and treeline danger to be HIGH.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Monday: 10-20 cm new snow expected with strong SW ridgetop winds gusting to 60 km/h. Treeline temperatures around -6C. Tuesday: up to 10 cm new snow. SW winds gusting to 45 km/h. Treeline temperatures around -7C. Wednesday: Dry. Light winds. Temperatures around -10C.

Avalanche Summary

A cycle of natural and human-triggered (including remotely-triggered and helicopter-remote) avalanches of up to size 2.5 was observed on Thursday and Friday across the region. The storm snow has been propagating easily on buried surface hoar and facets. Skiers recently triggered avalanches that resulted in wide propagation in the Shames Backcountry, highlighting the surprising reactivity of the snowpack.

Snowpack Summary

30-70cm of recent storm snow is bonding poorly to old snow surfaces, especially near Terrace. The old snow surfaces comprise of surface hoar crystals and/or facets. A few days ago, this layer was being triggered naturally or remotely and propagating widely. Near Bear Pass, reports indicate the storm snow may be bonding slightly better. Recent strong southwesterly to easterly winds have set up wind slabs in many exposed lee areas. There are two surface hoar layers in the upper snowpack. The upper one formed at the end of December and is buried on average 50 cm below the surface. This one is particularly reactive at present. The lower one formed at the beginning of December and is buried around a metre below the surface. There are no recent reports of activity on this layer. Near the base of the snowpack, a crust/facet layer continues to give hard, sudden results to no results in snowpack tests. This weakness is unlikely to be triggered by a single person, but it remains possible with a very heavy load (e.g. cornice fall) or from a thin-spot trigger point.

Avalanche Problems

Storm Slabs

Storm snow is bonding poorly with buried surface hoar buried around 50cm, creating a touchy storm slab problem. Wind slabs have formed predominantly on westerly and northerly aspects.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5