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Avalanche Forecast

Dec 24th, 2016–Dec 25th, 2016
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
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: Northwest Inland.

Use extra caution this holiday weekend as weak layers near the bottom of the snowpack have been very touchy. Stick to mellow terrain and avoid steep and convex slopes.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SUNDAY: Increasing cloud with afternoon flurries, southwest winds picking up throughout the day reaching 40 km/h by the afternoon and reaching 80 km/h overnight, temperatures around -15C.MONDAY: Stormy with accumulations of 5-15 cm, strong southwest winds, temperatures around -10C.TUESDAY: Flurries with trace accumulations, moderate west winds, temperatures around -10C.

Avalanche Summary

Persistent slabs have been very touchy in areas with thin snowpacks, as several size 1.5-2 avalanches have been remotely triggered the past few days. The avalanches have released on weak facets near the ground in steep shallow start zones. Remote triggering is a sign of a serious weakness deep in the snowpack and indicates that persistent slab avalanches may be triggered with very light loads. Also, strong winds with new snow will continue to develop wind slabs throughout the region on Sunday. Overall, human triggering remains likely, especially in terrain that has not been heavily ridden.

Snowpack Summary

Clear cold weather has limited the settlement of recent storm snow and resulted in the formation of new surface hoar and surface facets. Last week, extreme winds formed hard wind slabs behind exposed terrain features. Elsewhere, up to 50 cm of low density snow sits over a highly variable interface comprised of wind-scoured surfaces, hard wind slabs, faceted (sugary) snow, and feathery surface hoar in sheltered areas. The new snow appears to have bonded poorly to this interface. The snowpack is still shallow throughout the region and widespread faceting of the entire snowpack is likely in most areas. A thick rain crust that formed in early November is probably near the bottom of the snowpack and is likely surrounded by sugary facets. Basal facets and depth hoar (more sugary crystals) right at the bottom of the snowpack are reportedly widespread.

Avalanche Problems

Persistent Slabs

A substantial amount of recent snow has loaded two layers of weak, faceted snow: one is buried around 50 cm and the other near the base of the snowpack. Likely trigger points are unsupported (convex) slopes in shallower snowpack areas.
Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Avoid unsupported slopes.Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3

Wind Slabs

Triggering wind slabs remains possible in exposed lee areas, as last week's storm delivered up to 50 cm of new snow with strong winds.
Be aware of the potential for wide propagations due to the presence of hard windslabs.The new snow buries a weak layer which may increase the reactivity of new slabs.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2