Avalanche Forecast

Issued: Jan 2nd, 2012 9:24AM

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

Avalanche Canada jfloyer, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

A punchy, slow moving Pacific frontal system is tracking across this region, bringing moderate to locally heavy precipitation Tuesday to Thursday. Precipitation amounts of around 10 mm are anticipated for Tuesday, 20 mm for Wednesday, and 10mm for Thursday. Freezing levels will reach around 2000 m during Tuesday and Wednesday, dropping to around 1000 m on Thursday. Extreme ridgetop winds are predicted to gust to around 130 km/h from the SW Tuesday, to 110 km/h from the S on Wednesday and to 100 km/h from the SW on Thursday.

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

Strong winds have been the biggest story recently. Exposed windward slopes have been scoured and wind slabs have formed in lee terrain and may be susceptible to human triggering. There is now around 55-70cms of snow sitting on a surface hoar/crust/facet combo buried mid-December. This crust is widespread and exists in most start zones up to 2000m. Facets can reportedly be found above or below the crust. Prior to being buried, the surface hoar was destroyed by high winds in the alpine, but still coexists with the crust at treeline and below. Higher snow areas in the region have already seen an avalanche cycle on this layer-- these slopes will have been cleaned out nicely. More worrying are slopes where activity has not yet occurred--there are likely still dragons lurking out there. The midpack is well settled and strong.

Problems

Wind Slabs

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

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Storm Slabs

An icon showing Storm Slabs
Forecast new snow will set up storm slabs on open slopes at treeline and in the alpine.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 5

Persistent Slabs

An icon showing Persistent Slabs
Persistent slabs have now formed at all elevations where the mid December buried surface hoar/crust/facet layers exist. The probability of triggering has decreased, but the consequences of a release remain high.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Jan 3rd, 2012 8:00AM