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Archived

Avalanche Forecast

Feb 6th, 2018–Feb 7th, 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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Kootenay Boundary.

Forecast snow amounts vary through the region. If your local riding area receives less then 25 cm of new snow please consider the danger rating to be CONSIDERABLE on Wednesday.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Wednesday

Weather Forecast

Wednesday: Snow amounts 10-15 cm with alpine temperatures near -4. Ridgetop winds moderate from the west and freezing levels near 1500 m.Thursday: Snow amounts up to 30 cm accompanied by strong west winds. Freezing levels near 1500 m. Friday: mix of sun and cloud with freezing levels falling to valley bottom. Alpine temperatures near -12.

Avalanche Summary

Avalanche activity is ongoing through the region. On Monday, several natural storm slab avalanches and skier triggered avalanches up to size 2.5 were reported. These avalanches were mostly seen from NNE-E aspects above 1900 m. There was one deep persistent slab that pulled as a natural size 3.5. It ran full path to a historical run-out through 15 m worth of mature timber. This was reported from a east aspect at 2100-2300 m, running 900 m in length and up to 400 m wide. Looking forward with forecast snow and wind, expect newly formed storm slabs and the persistent slabs beneath them to remain reactive to human triggers with the potential for very large and destructive avalanches.

Snowpack Summary

Recent storm snow totals vary from 25-50 cm and the winds created reactive wind slabs at tree line and above. Forecast storm snow amounts vary but the region will see significant amounts by Thursday, adding stress to the underlying and very complex snowpack. Deeper in the snowpack, surface hoar and/or a crust from mid-January is buried beneath all the storm snow at 90-120cm deep. This interface has been reactive and this interface remains a concern. Below this layer lies a second crust/surface hoar interface buried early-January that is now 120-140 cm deep. Recent avalanches have stepped down to this layer and it should remain on your radar.The mid-December surface hoar layer is buried 130-170 cm below the surface. This layer has continued to produce step down releases and "sudden" test results. It is most pronounced at tree line and below treeline and has remains reactive especially in steeper, unsupported convex terrain features.

Avalanche Problems

Storm Slabs

Storm slabs will continue to build and be reactive with forecast new snow and strong winds.
Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid all avalanche terrain during periods of heavy loading from new snow and wind.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 3

Persistent Slabs

The snowpack is complex and continues to produce very large avalanches on several weak layers buried 80 to 150 cm below the surface. Moderate-angled, simple terrain selection remains critical to safe mountain travel.
Minimize overhead exposure; avalanches may reach the end of run out zones.Be mindful that deep instabilities are still present and have produced recent large avalanches.Good day to make conservative terrain choices.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 4