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Archived

Avalanche Forecast

Jan 9th, 2012–Jan 10th, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Northwest Coastal.

Confidence

Good - Timing, track, or intensity of incoming weather is uncertain on Thursday

Weather Forecast

A few more cm of new snow is expected on Monday night for Coastal and Interior regions. 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 Wednesday night or Thursday morning.

Avalanche Summary

Widespread avalanche activity along the highway corridors during Saturday night and Sunday morning. 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 on Sunday morning. 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

Another 10-20 cm of snow has added to the storm snow from Saturday night. The storm slab is now about 50-80 cm depending on elevation. 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.

Avalanche Problems

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: Possible - Likely

Expected Size: 2 - 6

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: Possible - Likely

Expected Size: 2 - 5