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Archived

Avalanche Forecast

Dec 2nd, 2018–Dec 3rd, 2018
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
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: Lizard-Flathead.

Uncertainty exists around the buried weak layers in the snowpack. Human triggers are still possible, especially where the slab sits above a weak layer. If the sun comes out, heads up on sun-exposed slopes for loose wet avalanches.

Confidence

Moderate - The weather pattern is stable

Weather Forecast

MONDAY: Cloudy in the morning with sunny skies in the afternoon/ alpine temperatures near -9/ generally light winds from the West/ freezing level valley bottomTUESDAY: Mix of sun and cloud/ alpine temperatures near -12/ ridgetop winds light from the West/ freezing level valley bottomWEDNESDAY: Sunny with some clouds/ alpine temperatures -12/ ridgetop winds light from the northeast/ freezing levels valley bottom

Avalanche Summary

On Sunday, a human triggered avalanche size 1.5 was reported. This ran on a northwest aspect at 2300 m. The crown was 15 cm, 20 m wide and ran 300 m. Explosive control also triggered a few storm slabs up to size 2 from northeasterly aspects 1800-2000 m. Check out the initial report here.On Monday, If the sun comes out the surface snow may become wet and deteriorate on sun-exposed slopes. Loose wet avalanches may occur.Even though the avalanche hazard has decreased I suspect human triggered avalanches will be possible, especially where the storm slab sits above a weak layer like surface hoar or the early November crust. If you're in the backcountry and have observations to share, please post to the Mountain Information Network.

Snowpack Summary

Up to 55 cm of recent snow sits on a series of crusts and a feathery surface hoar layer. A predominant crust can be found below this recent snow at treeline and into the alpine on all aspects. Reports indicate that the slab above this crust may be more reactive on northerly aspects. I would investigate this bond before jumping onto large, planar terrain features. We have a lot of uncertainty around this weak surface hoar layer, its distribution is spotty. I suspect that it could exist on sheltered slopes in the alpine and at treeline. At the bottom of the snowpack you'll likely find another crust and sugary weak facet crystals around it. At treeline the average snowpack depths are 80 cm. These depths taper rapidly at lower elevations.

Avalanche Problems

Persistent Slabs

55 cm of recent storm snow is consolidating into a slab above a crust and/or feathery surface hoar interface below. This crust is buried on all aspects at treeline and above and may be triggered by the weight of a human.
Watch for signs of instability, such as whumphing, shooting cracks, and recent avalanches.Triggering from a thin spot may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Loose Wet

If the sun comes out, sun-exposed slopes may see natural loose wet avalanche activity. Moist or wet snow surfaces are your initial indicator.
loose wet sluffs may step down to deeper layers resulting in large avalanches.Minimize exposure to steep sun-exposed slopes

Aspects: South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 1.5