Avalanche Forecast

Issued: Jan 3rd, 2012 9:44AM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Wind Slabs, Storm Slabs and Persistent Slabs.

Avalanche Canada jfloyer, Avalanche Canada

Summary

Confidence

Good - -1

Weather Forecast

An intense storm will bring moderate to local heavy amounts of precipitation-expect around 15-20 mm Tuesday night and a further 5-15 mm on Wednesday. Freezing levels will rise to around 1500 m and then start to fall on Wednesday afternoon as a cold front passes over. The passage of the cold front is unlikely to bring only light precipitation to inland areas, say 5 mm. Ridgetop winds will be extreme (up to 140 km/h) initially from the southwest, then becoming westerly. On Friday, another frontal system hits the north coast; however it looks as though northwest inland areas will be influenced by a ridge of high pressure keeping things mainly dry and cold.

Avalanche Summary

High winds and poor visibility have limited observations for the last few days; however, no activity has been reported to us from this region recently. I suspect you could easily trigger a pocket of wind slab on exposed lee terrain and I'd still be nervous of triggering the mid-December surface hoar layer down around 70 cm in sheltered locations.

Snowpack Summary

New snow and strong winds have set up fresh wind slabs mainly on north through east aspects in exposed lee terrain--these are likely triggerable by riders on sleds or on skis. There is now approximately 80 to 120cms of storm snow sitting above a surface hoar/crust/facet layer that was buried mid-December. The increasing depth of this weak layer makes it difficult to trigger; however, I wouldn't ignore this layer yet, as it could still be triggered by large loads such as rapid loading by new snow or rain or cornice falls. It could also be triggered by riders in shallow snowpack areas or where rocks poke up near the surface. The mid- and lower snowpack layers are well consolidated and generally strong.

Problems

Wind Slabs

An icon showing Wind Slabs
Strong southwesterly winds continue to set up touchy wind slabs on mainly north through east aspects.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

2 - 5

Storm Slabs

An icon showing Storm Slabs
New snow with rising temperatures will set up storm slabs on steep, open slopes.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

2 - 6

Persistent Slabs

An icon showing Persistent Slabs
Persistent slabs are getting harder to trigger but still exist in many locations. The probability of triggering has decreased, but the consequences of a release remain high.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 7

Valid until: Jan 4th, 2012 8:00AM