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Archived

Avalanche Forecast

Feb 18th, 2016–Feb 19th, 2016
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
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Northwest Inland.

Recently formed storm slabs and wind slabs will continue to be reactive to human-triggering on Friday and conservative terrain selection remains very important.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Unsettled conditions are expected for Friday with periods of light snowfall and sunny breaks. Alpine winds are expected to be moderate to strong from the southeast and freezing levels are forecast to reach around 1000m in the afternoon. Dry conditions with a mix of sun and cloud is expected for Saturday with moderate southerly winds in the alpine and freezing levels around 700m. A mix of sun and cloud is currently forecast for Sunday morning with a weak storm pulse arriving Sunday evening.

Avalanche Summary

On Wednesday, two size 1 wind slabs were skier triggered. Both were wind-loaded features at treeline and one was reported to be 20cm thick. On Tuesday, a size 1 storm slab was ski cut on a convex roll at treeline. Recently formed storm and wind slabs are expected to remain reactive to human-triggering on Friday. If the sun comes out, natural avalanches are possible on steep south facing terrain features. In the far north, deeply buried persistent weak layers may still be reactive to large triggers such as a small avalanche stepping down or a cornice failure.

Snowpack Summary

40-80cm of snow has accumulated over the past week and overlies a melt freeze crust which extends up to around 2000m elevation. This recent snow is reported to be bonding well to the crust. Moist snow was reported below 1200m on Wednesday and wet snow below 800m. Recent wind has redistributed the surface snow at higher elevations forming wind slabs in leeward features. The early January surface hoar/facet layer is down around 1m+ and remains a concern for commercial operations. This layer seems the most reactive in the north of the region but may still be a concern in the south as well. Shallow snowpack areas in the east and north of the region may have a weak base layer of facetted snow on or just above the ground.

Avalanche Problems

Storm Slabs

Recently formed storm slabs are expected to be reactive to human-triggering on Friday. Wind loaded alpine features are likely to have the most reactive slabs.
The new snow will require time to settle and stabilize. >Stay off recent wind loaded areas until the slope has had a chance to stabilize. >Be alert to conditions that change with elevation. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Deep Persistent Slabs

Buried weak layers are still reactive in the snowpack, especially in the far north of region, and have the potential to produce very large avalanches. Thin spot triggering, cornice releases, and smaller avalanches all have the potential to step down.
Avoid convexities or areas with a thin or variable snowpack.>Be aware of the potential for large, widely propagating avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 6