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Avalanche Forecast

Jan 29th, 2018–Jan 30th, 2018
Alpine
4: High
The avalanche danger rating in the alpine will be high
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

Significant uncertainty exists with forecast snowfall amounts: If you see more than 30 cm of new snow, consider the danger to be HIGH and avoid all avalanche terrain, including overhead hazard.

Confidence

Low - Intensity of incoming weather systems is uncertain

Weather Forecast

Tuesday: 5-15 cm snow Monday overnight into Tuesday with another 10 cm snow possible during the day. Light to moderate south-westerly winds. Alpine temperature near -6. Wednesday: Cloudy with isolated flurries. Light south-westerly winds. Alpine temperature near -8.Thursday: Occasional flurries. Moderate south-westerly winds. Alpine temperature near -8.More information can be found in the Mountain Weather Forecast.

Avalanche Summary

On Saturday near Kimberley, skiers remote-triggered two Size 2 avalanches, by a convex roll near 2000m elevation. Crown height was 60-70cm, suggesting the snow ran on the mid January layer. See the MIN report for more details. With consistent loading into Tuesday, human triggering will remain likely and avalanches could be surprisingly large due to the structure of the snowpack.

Snowpack Summary

The current snowpack is complex, with three active weak layers that we are monitoring.1) 60-90 cm of recent storm snow overlies a crust and/or surface hoar layer (from mid-January). The crust is reportedly widespread, except for possibly at high elevations on north aspects. The surface hoar is 10 to 30 mm in size, at all elevation bands. The recent snow fell with strong south winds, producing wind slabs and cornices in lee features. 2) Deeper in the snowpack (down 70-100 cm), a persistent weak layer known as the early-January layer is present at all elevation bands, and composed of surface hoar on sheltered slopes and sun crust on steep solar aspects. Recent snowpack tests have shown sudden fracture characters with moderate loads and high propagation potential. 3) Another persistent weak layer that was buried mid-December is 80 to 120 cm deep and consists of a facet/surface hoar/crust combination. It is most problematic at and below tree line.A rain crust buried in November is 100 to 150 cm deep and is likely dormant for the time being.

Avalanche Problems

Storm Slabs

Forecast moderate winds, heavy snowfall and warming temperatures are a recipe for widespread avalanches. A storm slab could step down to a deeper weak layer, creating a surprisingly large avalanche.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.If triggered storm slabs may step down to deeper layers and result in very large avalanches.The new snow will take time to settle and stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 3

Persistent Slabs

Several weak layers are buried in the snowpack, creating very large avalanches when triggered.
Use conservative route selection, bearing in mind that avalanches may be surprisingly large.Avoid thin, rocky or sparsely-treed slopes.Avoid open slopes and convex rolls where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 4