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Archived

Avalanche Forecast

Feb 11th, 2013–Feb 12th, 2013
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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

Good

Weather Forecast

Synopsis: A frontal system moves through the region late on Tuesday bringing light snowfall Tuesday night. On Wednesday afternoon and Thursday, a ridge of high pressure builds in the region.Tuesday: Flurries. Light SW winds increasing at the end of the day. Freezing level around 1000m.Wednesday: Around 5 cm new snow, which should end by noon. Clearing in the afternoon. Freezing level around 1200m. Strong westerly winds in the morning, diminishing through the day.Thursday: Dry and sunny. Freezing level 800m in the afternoon. Light NW winds.

Avalanche Summary

There were two size 1 human-triggered avalanches reported from Saturday on north aspects in recent new snow with crowns of 10-20 cm. Loose snow avalanches were reported over the weekend on steep solar aspects. On Sunday, several small (size 1) human-triggered avalanches were reported in buried surface hoar from just outside the region on north aspect slopes.

Snowpack Summary

The snow surface consists of a sun crust, surface hoar, or a dusting of new snow. Below this approximately 15-20 cm of recent storm snow has been redistributed into soft wind slabs at higher elevations. The new snow overlies a gamut of old surfaces which include old wind slabs at higher elevations, fairly widespread surface hoar, and a melt-freeze crust on previously sun-exposed slopes. This interface will be something to watch as the overlying slab develops. About 35-50cm below the surface is another interface of surface hoar or a sun crust that was buried on Jan 23. It is hard to find in some areas and seems to be gaining strength where it is found, but this weakness is still on the radar of professionals in the region. The snowpack below this is generally well settled and bonded.

Avalanche Problems

Wind Slabs

Triggering is possible on steep gully sidewalls and in the lee of ridge crests.
Watch freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Persistent Slabs

An assortment of weak crystals is buried between 35 and 50cm below the surface. Although this interface is gaining strength, triggering may still be possible in unsupported terrain.
Dig down to find and test weak layers before committing to a line.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 1 - 4