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Archived

Avalanche Forecast

Feb 10th, 2015–Feb 11th, 2015
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
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
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: Glacier.

Human triggering of avalanches remains likely and conservative terrain selection is critical. If the sun breaks through the clouds natural avalanches are possible. Minimize exposure to overhead avalanche terrain and slopes threatened by cornices.

Weather Forecast

Generally mild conditions will continue. The forecast is for mostly cloudy skies with light flurries. Sunny breaks are possible especially at higher elevations. The sun may destabilize the new snow, and avalanches are possible during sunny periods. Freezing levels are ~1300m and moderate W'ly winds are expected at ridgetop.

Snowpack Summary

Up to 20cm of dry snow has buried moist snow from the weekends rain. 140cm have fallen since Feb 1 and settled to ~1m of settled storm snow over the Jan 30 layer. This layer formed a crust to 2200m with spotty surface hoar distribution. Jan 15 surface hoar layer is down 100-150cm and continues to be reactive in tests.

Avalanche Summary

Rain switched to snow yesterday and avalanche activity tapered off. Since Thursday, a large avalanche cycle occurred with avalanches to size 3.5 running from all elevations into valley bottoms. Reports from skiers in the region are of touchy conditions, with remote triggering of slabs up to 1m deep and wide propagations.

Confidence

Timing or intensity of solar radiation is uncertain

Avalanche Problems

Storm Slabs

A warm, wet and windy storm over the weekend created a storm slab that is up to 1m deep. On lee slopes, wind loading may have made this slab much deeper and more reactive. 
The new snow will requires several days to settle and stabilize.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Persistent Slabs

Persistent weak layers within the top 150cm of the snowpack should not be forgotten. They continue to be reactive, and produce very large avalanches. Storm slabs avalanches may step down and propagate on these deep instabilities.
Avoid shallow snowpack areas where triggering is more likely.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 4