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Archived

Avalanche Forecast

Jan 8th, 2013–Jan 9th, 2013
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
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
3: Considerable
The avalanche danger rating below treeline will be considerable
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: Purcells.

Cautious travel practices, and conservative decision making is essential through the forecast period.

Confidence

Fair - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

Wednesday: Cloudy with lingering snowfall. Expect 20-40cm of total accumulations, with the higher amounts in the southern portion of the region. Winds should be strong southwesterlies with freezing levels climbing to 1300m.Thursday: There is a chance of continued flurries, with westerly winds abating and temperatures falling to -13.Friday: Expect mixed skies with light winds and cool temperatures.

Avalanche Summary

Small windslabs up to size 1.5 have been reported, failing in immediate lee locations of ridgelines and isolated storm slabs have been reported to 1.0. Sluffing up to size 1.5 continues.

Snowpack Summary

On the west side of the region up to 50cm of new snow overlies the January 4th interface while on the east side the new snow totals around 10-20cm. Consistent moderate and strong south/southwest winds have redistributed this new snow into windslabs in lee features in the alpine and exposed treeline and these windslabs are reactive to human triggering. In some areas the windslabs extend lower down the slope than normal due to locally extreme winds.The January 4th interface consists predominantly of loose facets. In isolated locations (sheltered treeline and below treeline) surface hoar is present and there is a sun crust on steep south and west facing terrain. In some areas the new snow is bonding poorly to these interfaces, and lots of sluffing is being reported. Where the storm snow is deeper (around 30cm), the sluffing is extensive enough to require a management plan. The deepest deposits of storm snow (pushing 50cm) are settling into a more cohesive storm slab. The midpack is well bonded and strong. The deep crust/facet combo from early November still exists and concern remains (although unlikely) for triggering this layer from a shallow spot.

Avalanche Problems

Wind Slabs

The consistent strong winds mean that the windslabs extend lower into the terrain than normal.
Avoid freshly wind loaded features.>

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

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 6

Storm Slabs

As the storm snow gets deeper, the slab will become more cohesive and reactive.
The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4

Cornices

Strong winds and lots of new snow makes perfect conditions for cornice growth. These are a hazard by themselves but can also trigger avalanches on slopes below.
Do not travel on slopes that are exposed to cornices overhead.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 2 - 5