Avalanche Forecast

Issued: Dec 1st, 2021 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Loose Wet and Wind Slabs.

Avalanche Canada zryan, Avalanche Canada

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Watch out for fresh wind slabs forming in the alpine with cooling temperatures overnight. Colder temperatures will help decrease loose wet avalanche activity, but steep slopes will remain a likely place for human triggering.

Summary

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Wednesday overnight: 2500m freezing levels will begin to descend, reaching 1800m by morning. Another 10-20mm can be expected, initially falling as rain, and eventually falling as snow at higher elevations. Winds will continue to be strong to extreme from the southwest. 

Thursday: A clearing trend! Up to 15cm of mixed precipitation can be expected in the early morning, with freezing levels sitting around 1700m. Throughout the day, we will see clearing skies, lowering freezing levels, and winds steadily decreasing into the moderate to strong range from the west. 

Friday: High pressure prevails. A mainly sunny day with light winds from the southwest and freezing levels at valley bottom. Another front is on its way in the afternoon, so high clouds may form in the afternoon.

Saturday: Another system is upon us. 10-20cm of snow is expected, with the possibility of locally higher accumulation with upslope enhancement. Freezing levels rising up to 1500m.

Avalanche Summary

There have been very few reports in the past 24 hours. I suspect a widespread natural avalanche cycle has occurred in conjunction with Wednesday's storm. 

Reports from the region remain limited. If you go out in the mountains, please share your observations and/or photos on the Mountain Information Network! 

Snowpack Summary

Heavy rain has soaked the upper snowpack at most elevations. In the high alpine (above 2300m), up to 50cm of wet snow accumulation is possible. Until temperatures cool, this will result in a wet, heavy, and unstable upper snowpack.

Two crusts are found in the snowpack: the mid-November rain crust buried 20-30 cm and reported up to 2100 m, and a crust from early November found at the bottom of the snowpack up to 2300. This crust is beginning to break down and facet. Heavy loading by Wednesday's storm will answer our questions about the potential for failure at this layer.

Snowpack depths range from 40-120cm at treeline elevations. Higher elevations may hold a deeper snowpack, but will also be more heavily impacted by recent winds. Snowpack depths decrease rapidly below 1900 m.

Terrain and Travel

  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

Problems

Loose Wet

An icon showing Loose Wet

Wednesday's storm brought significant rain that saturated the snowpack. Cooling temperatures will help to decrease the likelihood of loose wet avalanches, but steep slopes will remain likely places for wet loose avalanches to occur - especially with a human trigger. 

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Wind Slabs

An icon showing Wind Slabs

Heavy precipitation on Wednesday night may turn to snow up high and create a wind slab problem in the alpine. If dry snow exists in the alpine, watch out for cracking, whoomphing and wind transportation. 

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 2nd, 2021 4:00PM

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