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Archived

Avalanche Forecast

Dec 4th, 2012–Dec 5th, 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
3: Considerable
The avalanche danger rating at treeline will be considerable
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
1: Low
The avalanche danger rating below treeline will be low

Regions: Purcells.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Overnight and Wednesday: Light to locally moderate snowfall overnight, easing off by late Wednesday / Strong to extreme southwest winds / Freezing level at 1000m dropping to surface by WednesdayThursday: Light snowfall / Moderate west winds / Freezing level at 900mFriday: Possibility of clearing / Light southwest winds / Freezing level at surface

Avalanche Summary

On Monday whumphing and cracking was observed in the Invermere area between 2150m and 1850m. A slab avalanche (50cm deep/ 15-20m wide) was ski cut in the same area on a north aspect between 1900 and 2000m. It was suspected to have run on the early November faceted rain crust. Any field observations can be sent to [email protected].

Snowpack Summary

Strong winds and light to locally moderate snowfall are responsible for newly formed wind slabs which are likely to exist at treeline and above. Over the last few days snowfall amounts have been highly variable throughout the region; however, reports indicate that up to 60cm of recent storm snow may sit above a surface hoar layer that was buried on the 28th. Although not widespread in the region, releases on this layer are likely if you have it in your area. A surface hoar layer that developed during mid-november may exist up to 85cm down, but has not been reactive during the recent storm. There is a rain crust near the ground that we're calling the early November crust. There are some facets below it, or it may appear as a sandwich of crusts and facets, but it's been reported as unreactive at this time. There is still a sharp transition in snow depth from treeline to below treeline making back-country travel challenging under 1300 m in elevation.Significant variations in snowpack structure exist across the region. Digging down and making your own observations will be critical to safe slope selection.

Avalanche Problems

Storm Slabs

Forecast snowfall and extreme winds will create new wind slabs and potentially add to the reactivity of a storm slab that may sit over weak surface hoar crystals. With expected wind values, loading may occur lower on the slope than normal.
Be aware of the potential for wide propagations due to the presence of hard windslabs.>Be alert to conditions that change with elevation.>

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

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4

Persistent Slabs

Two problem layers exist: A surface hoar layer 40 - 85 cm below the snow surface and the early November crust near the ground. It may be possible for a rider to trigger these weak layers, especially in areas where the snowpack is thin and/or rocky.
Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 5