Avalanche Forecast
Issued: Dec 11th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
ahanna,
Avalanche Canada
Watch for small solar triggered loose dry avalanches in steep terrain where direct sun grazes dry snow for the first time.
Summary
Confidence
Weather Forecast
Friday night: Isolated flurries, moderate northerly ridgetop wind, freezing level valley bottom.
Saturday: Sunny, light variable ridgetop wind, alpine high -2C, freezing level 500 m.
Sunday: Sun and cloud, moderate southwest ridgetop wind, alpine high -6C, freezing level 500 m.
Monday: Sun and cloud, light to moderate southwest wind, alpine high -5C, freezing level 600 m.
Avalanche Summary
Since Wednesday, natural avalanche activity has been limited to loose dry sluffs of diminishing size.
A widespread natural cycle occurred during the storm Monday night through Tuesday, storm slabs size 2-3 and loose wet size 1-2.
On Tuesday December 1, a large size 3 natural avalanche was observed on a NE aspect at 2400 m in the Duffy area. It was reported as a cornice failure triggering the slope below and appeared to have slid on the early November crust near the base of the snowpack.
Have you been out and about in the mountains? If so please submit your observations to the Mountain Information Network (MIN). It doesn't have to be technical - photos are especially helpful! Thank you so much for all the great MINs submitted so far!
Snowpack Summary
- In the south, 10-20 cm of dry surface snow bonds to the underlying crust formed earlier this week when 25 mm of rain soaked the upper snowpack at all elevations. We've got our eye on a couple of crusts in the upper to mid snowpack that are producing moderate to hard snowpack test results. Treeline snowpack depth sits around 80-130 cm.
- In the north, around 30 cm of recent snow sits over a thin zipper crust above 2300 m, snow tapering with elevation. Between 1600 and 2000 m, the crust is punchy and unsupportive. In the lower snowpack, a crust/facet layer sits near the ground. The most recent avalanche observed on this layer was on December 1st, while recent snowpack tests in the Cayoosh zone found this layer down 60 cm and unreactive. We have a lot of uncertainty on the reactivity of this layer so we're keeping it on our radar.
Terrain and Travel
- A crust on the surface will help bind the snow together, but may make for tough travel conditions.
- Be alert to conditions that change with elevation.
- Minimize exposure to sun-exposed slopes when the solar radiation is strong.
- Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.
Problems
Storm Slabs
Loose dry avalanches are likely where the sun touches dry snow for the first time. You may also find small pockets of triggerable storm slab near ridgetops.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Deep Persistent Slabs
A crust/facet layer sits near the base of the snowpack. It is surrounded by weak crystals and produces hard results in snowpack tests. In shallow, rocky areas in the alpine, it may remain at a depth triggerable by humans. Last week a natural cornice fall triggered a size 3 avalanche on this layer proving it's still a player. With the cooling temperatures and hardening snowpack, we don't think we will see avalanche activity on it at the moment, but it's definitely still on the radar.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 12th, 2020 4:00PM
