Avalanche Forecast

Issued: Dec 5th, 2012 9:50AM

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 Deep Persistent Slabs.

swerner, Avalanche Canada

Cariboos.

Summary

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

Thursday: The region will be under the influence of a Westerly zonal flow. This will bring cooler temperatures, mix of sun and cloud and light snow amounts daily. Friday through Saturday: A weak ridge sets up over the coast bringing an even dryer, cooler NW flow. Freezing levels will remain in valley bottoms, alpine temperatures steady -10 falling to -15 on Saturday. The next hit of precipitation is expected Sunday, as a Pacific frontal system moves across the region.

Avalanche Summary

There are limited recent observations from this Region. I suspect a natural avalanche cycle may have occurred. The weight of a human rider is likely to trigger avalanches at treeline and above, especially on wind loaded aspects and behind terrain features.Any observations from the field are welcome at forecaster@avalanche.ca.

Snowpack Summary

New snow 40-60 cm fell over the past 4 days blankets the region. Instabilities (surface hoar layer, and a thin sun crust) may exist within or down 40-60 cm. We have very limited information on the extent or sensitivity of these layers, but suspect them to be reactive under the load of the new snow. A second buried surface hoar layer, down about 115 cm, and the early November rain crust (facet-crust combo), over 140cm down in some locations, remain a concern for isolated deep slab avalanches.Average snow depths at treeline seem to be between 140cm and 180cm. Elevations below 1500m are still reported as below threshold.In general, snowpack data is sparse in this region and significant variations likely exist from one drainage to another. Digging down and making your own observations will be critical to safe slope selection.

Problems

Wind Slabs

Deep and dense wind slabs are likely in exposed lee slopes and cross-loaded gullies well below ridge crests.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Avoid lee and cross-loaded terrain near ridge crests.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Storm Slabs

Instabilities may exist within or under the recent storm snow (up to 60cm) and may be triggered naturally or by the weight of a person.

Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>Be aware of the potential for large avalanches due to the presence of old buried layers.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Deep Persistent Slabs

Although the likelihood of a release is low, the consequences of a persistent slab release could be significant. These layers may wake-up with additional loading.

Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Dec 6th, 2012 2:00PM