Archived

Avalanche Forecast

Dec 1st, 2017–Dec 2nd, 2017

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

1: Low

The avalanche danger rating below treeline will be low

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

Regions: Lizard-Flathead.

Reactive storm slabs will likely exist at treeline and in the alpine. With limited observations and a variable snowpack use a conservative approach to route selection.

Confidence

Low - Forecast snowfall amounts are uncertain

Weather Forecast

Saturday: Mostly cloudy with snow amounts 10-25 cm and ridgetop winds moderate from the South West. Alpine temperatures near -8. Freezing levels 1100 m. Sunday: Mostly cloudy with isolated flurries. Ridgetop winds light from the West. Alpine temperatures -8 and freezing levels near 800 m. Monday: Mostly sunny with ridgetop winds light from the West. Alpine temperatures near -10 and freezing levels at valley bottom. Uncertainty around the snowfall amounts overnight Friday and Saturday.

Avalanche Summary

On Friday, explosives control saw numerous storm slab avalanches up to size 2 on N-NE aspects above 2000 m. We suspect these avalanches are running on the November 27th crust. Storm slabs and wind affected snow on leeward slopes may be reactive to rider triggers through the weekend. Please submit your observations this weekend to the Mountain Information Network. Give info, get info.

Snowpack Summary

Up to 40 cm of accumulated storm snow has fallen on the crust that formed last week. The buried crust is supportive and approximately 10 cm thick. It extends from 1600 m to mountain top elevations on all aspects. Reports indicate that the recent storm snow may have a poor bond to the crust. Ridgetop winds are likely redistributing the new snow above treeline and possibly forming wind slabs on leeward slopes and terrain features. The average snowpack depth at treeline is 60-80 cm while a deeper snowpack exists in the alpine. The snowpack remains highly variable in regards to aspect and elevation.

Avalanche Problems

Storm Slabs

Storm slabs may have a poor bond to a buried crust down 30-60 cm and will likely be reactive to rider triggers. Winds have redistributed the new snow forming thicker slabs on leeward features above 1600 m.

Be careful with wind loaded areas, especially near ridge crests and roll-overs.Limited observations, use a conservative route selection, moderate angled and supported terrain.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2