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Archived

Avalanche Forecast

Jan 16th, 2017–Jan 17th, 2017
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
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.

A sudden change in weather can have surprising effects on the snowpack. Conservative terrain use is key.

Confidence

-

Weather Forecast

MONDAY NIGHT: Snow starting in the afternoon with trace accumulations in the south and up to 10 cm of new snow overnight in the north, wind increasing to moderate from the southwest, temperatures increasing overnight.TUESDAY: Snow continuing throughout the day with another 5-15 cm, moderate southwest winds, freezing level rising with alpine temperatures around -2 in the north and -5 in the south.WEDNESDAY: Flurries with another 5-10 cm of new snow, moderate south winds, freezing level rising to around 1500 m throughout the region.THURSDAY: Cloudy with isolated flurries, moderate southwest winds, freezing level around 1500 m.

Avalanche Summary

Avalanche reports from the weekend included several size 1 loose dry avalanches on a variety of aspects, and a few isolated size 1.5 wind slabs triggered on northeast aspects by explosive and natural triggers. On Tuesday, expect the new snow to build fresh and touchy storm slabs. Warming and loading will also increase the likelihood of triggering persistent slab avalanches.

Snowpack Summary

Expect 10-20 cm of new snow on Tuesday with greater accumulations in the northern part of the region. The new snow, wind, and warming will build touchy storm slabs that will be extra thick and reactive on wind-loaded features. In sheltered areas, the new snow is burying a layer of feathery surface hoar that may produce surprisingly wide propagations. The main concern deeper in the snowpack is a layer of sugary facets from mid-December that can be found between 50 and 100 cm deep. This layer was considered dormant during the recent cold weather, but may become reactive as warm temperatures soften the overlying slab.

Avalanche Problems

Storm Slabs

Fresh storm slabs will build throughout the week and be reactive to human triggers. Be extra cautious in wind affected terrain.
Minimize exposure during periods of heavy loading from new snow and wind.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2

Persistent Slabs

Rapid warming of the snowpack will increase the likelihood of triggering persistent weak layers that have been lingering deep in the snowpack.
Be cautious in shallow snowpack areas where triggering is more likely.Avoid steep, open slopes.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3