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Archived

Avalanche Forecast

Apr 12th, 2013–Apr 13th, 2013
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
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
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: Purcells.

Snowfall amounts for Friday night are uncertain. Danger could spike to HIGH by Saturday if we get more than forecast.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Saturday: Overnight snowfall tapering off to a cool and unsettled flow with light snow. Moderate W winds. Freezing level around 1000 m.Sunday: Cold and unstable weather, with light snow. Light N winds. Freezing level around 1000 m.Monday: Cold and unstable weather, with light snow. Light or calm winds. Freezing level around 1500 m.

Avalanche Summary

Observations have been limited during Wednesday’s storm, when a natural avalanche cycle is expected to have occurred. On Thursday, a cornice fall triggered a size 2.5 slab. Skiers also triggered size 1 slabs. These events were on NE aspects above 2300 m.

Snowpack Summary

Snowfall on Friday night is expected to create new storm/wind slabs, especially near ridge top. This will add to existing storm slab and wind slab problems at alpine and treeline elevations. A surface hoar interface is buried within the upper metre of the snowpack, mainly on high-elevation northerly aspects. It is still producing moderate, sudden results in snowpack tests, and these slopes should be treated with suspicion. On other slopes, recent storm snow overlies a crust, with a variable bond. At low elevations, previously rain-soaked snow is likely to now be refrozen and strong.

Avalanche Problems

Storm Slabs

Snowfall on Friday night is expected to create new storm slabs, especially near ridge top and on slopes in the lee of the wind.
Avoid freshly wind loaded features.>Choose well supported terrain without convexities.>Pay attention to overhead hazards like cornices.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Persistent Slabs

A layer of surface hoar is buried about a metre down, mainly on high northerly aspects. A surface avalanche stepping down, cornice fall, or the weight of a person from a thin-spot trigger point could trigger it.
Carefully evaluate and use caution around thin snowpack areas.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood: Unlikely - Possible

Expected Size: 1 - 6