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Archived

Avalanche Forecast

Mar 6th, 2012–Mar 7th, 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
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.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Until yesterday the weather story was all about snow with the last storm starting warm and finishing cold. Monday overnight a cold front came through. Looking forward the story for Wed & Thurs is sunshine - warm temperatures and SOLAR WARMING. Freezing overnight. Friday becoming cloudy, maybe flurries ahead of the next forecast system.

Avalanche Summary

Poor visibility most of the day limited observations. In the west side of the region reported avalanches were smaller and seem to be limited to the storm snow. In the east, where more storm snow fell avalanches were much larger. For example near Wyndell a large natural slide buried a sled access road near valley bottom. Some remotely triggered and accidentally triggered slides reported by skiers that were 70 to 100 cm deep. Neighbouring areas reported a widespread, large avalanche cycle and I'd be surprised if something similar didn't occur in the eastern part of the region. Looking forward I think we'll see some surprising avalanches triggered by warm temperatures & sun over the next few days as the snowpack slowly adjusts to this past storm.

Snowpack Summary

Freezing level somewhere around high below treeline or low treeline elevations (say 1600m or so) meant rain below and snow above. The west received another 10 cm while the east saw as much as 40 cm on Monday. I'd guess the storm snow total is around 70 cm. Valentines Surface hoar layer now buried beneath as much as 120 to 140 cm! Stability tests show the deep layers are hard to trigger but there's huge potential for propagation.

Avalanche Problems

Persistent Slabs

Persistently weak buried surface hoar demands continued diligence and conservative decisions. The potential for remote triggering, step down avalanches, and wide propagations, makes this weakness particularly tricky to predict. Watch cornices.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 3 - 6

Storm Slabs

Formally touchy weaknesses within the recent storm snow likely gaining strength, but remain a concern on both convex & unsupported features. It'll take a bit of time for the pack to adjust to this last storm. Solar radiation could trigger a surprise.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 4

Wind Slabs

Generally lurking below ridgecrests, behind terrain breaks, and in gullies. Wind slabs likely need a bit more time to settle out and gain strength. Shifting winds mean they may be in unusual places.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 4