Avalanche Forecast

Issued: Jan 8th, 2012 9:27AM

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

Avalanche Canada triley, Avalanche Canada

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

Drizzle in the valley will bring another 3-5 cm to higher elevations on Sunday night. The wind is expected to decrease to about 30 km/hr at the ridge tops by Monday morning. Some light snowfall accumulating a couple more cm on Monday until about noon around Terrace. Smithers is expected to be quite a bit drier; Sunday night and Monday precipitation combined should only be about 5 cm. Temperatures are expected to drop to about -15 in the alpine by Tuesday morning as a ridge of high pressure moves into the region. Wednesday is expected to be mostly clear, but not as cold as Tuesday. The next system should be on the coast by Thursday. There may be some strong outflow winds on Tuesday afternoon as cooler air moves out towards the Pacific.

Avalanche Summary

Widespread avalanche activity along the highway corridors. Size was limited due to storm and avalanche cycle earlier in the week. Size 4.0 natural on Mt Rainey ran to valley bottom adjacent to Stewart Town site. Widespread natural activity in the Shames area, possibly up to size 3.0 in the "Valley of Doom". Due to poor visibility we do not have any observations from alpine terrain.

Snowpack Summary

Very heavy precipitation on Saturday night brought at least 40 cm to lower elevations, and probably 60-80 cm in the alpine. Very strong southwest winds have probably transported this new storm snow into thick windslabs and storm slabs. This new storm layer is sitting on top of a storm layer from earlier in the week that did not have a lot of time to settle and strengthen. A relatively thin layer of surface hoar or facets was reportedly buried New Year's day - this may have been the focus of some of the storm snow releases during the current storm; however, I suspect this layer will settle out quite rapidly. Lower down, it is still possible to find a surface hoar/crust/facet combo from mid-December. I suspect it would take a very heavy trigger such as a cornice fall to trigger this layer now, although if you are traveling in an unusually shallow snowpack area I'd still be cautious of it. The lower snowpack is generally well settled and strong.

Problems

Storm Slabs

An icon showing Storm Slabs
The storm deposited a thick layer of new snow in areas that are protected from the wind, that may take a couple of days to bond to the old surface.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

3 - 7

Wind Slabs

An icon showing Wind Slabs
Wind slabs that developed during the storm will take a couple of days to settle and strengthen.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

3 - 6

Wet Slabs

An icon showing Wet Slabs
Wet slab avalanches and glide releases may continue to be touchy until the freezing level drops back down to the valley on Monday evening.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

3 - 6

Valid until: Jan 9th, 2012 8:00AM

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