Archived

Avalanche Forecast

Dec 10th, 2012–Dec 11th, 2012

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

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

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Kootenay Boundary.

Confidence

Fair - Intensity of incoming weather is uncertain on Tuesday

Weather Forecast

Overnight and Tuesday: A warm front is moving across the region tonight and a trailing cold front should move through the region in the morning. The North of the region should get 5-10 mm starting in the early morning. The South may be quite a bit drier (4-6 mm). Strong NW winds overnight should become moderate to strong Westerly during the storm. Alpine temperatures should be -9.0 and the freezing level may rise to 700 metres during the storm.Wednesday: There is a weak ridge between systems that should bring very light precipitation, light Northerly winds and temperatures down to -10.0 in the alpine.Thursday: The next frontal system is looking weak at this time. Expect light precipitation and SW winds. Check back tomorrow for an update.

Avalanche Summary

Some very soft slab avalanches up to size 1.5 were reported near Nelson from explosives control.

Snowpack Summary

There has been a lot of unconsolidated surface snow that has been producing heavy sluffing in steeper terrain. It sounds like the wind is starting to transport some of this light surface snow into wind slabs. If the wind has not affected the snow yet, it probably will by morning. There is still concern in this region for the late November surface hoar that is buried about 100-125 cms. New wind slabs and the recent storm snow may be enough of a load to make this weakness reactive to light additional loads. There was some discussion about a thin variable crust that formed around the 5th of December. We have not heard any concern about this lately, do you see it in your local area?

Avalanche Problems

Storm Slabs

There is a soft slab on the surface that may stiffen with wind transport over night. These slabs may be triggered by light additional loads like a skier or rider.

Avoid freshly wind loaded features.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4

Persistent Slabs

The buried surface hoar layer from late November may become reactive from the additional load of new snow and wind transported snow.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid open slopes and convex rolls where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 5