Avalanche Forecast
Issued: Jan 17th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
ahanna,
Avalanche Canada
Give those big saggy cornices an extra wide berth when the sun is shining. Avalanche hazard may be a step lower in the south of the region where deep weak layers are not a concern.
Summary
Confidence
Weather Forecast
Sunday night: Partly cloudy, light to moderate northwest ridgetop wind, freezing level 500 m.
Monday: Sunny, light to moderate northerly ridgetop wind, freezing level 1000 m.
Tuesday: Mix of sun and cloud, southwest ridgetop wind building to strong, freezing level 800 m.
Wednesday: Mix of sun and cloud, light northwest ridgetop wind, freezing level 600 m.
Avalanche Summary
Natural cornice falls up to size 2 have been observed recently. Explosive control work on Friday produced wind slab avalanches up to size 2.
A widespread natural avalanche cycle size 2-3 occurred throughout the region during a storm last week. Avalanche character was predominantly storm slab in the snowy north of the region and wet loose or glide slab in the rainy south. Northwest of Pemberton, several stepped down to buried weak layers resulting in very large (size 3-4) persistent slab avalanches.
Snowpack Summary
In the south of the region, fluctuating freezing levels during the last storm have resulted in a crust to ridgecrest. At upper elevations, 5-10 cm of dry snow has been blown around by the wind, exposing the crust in some areas and building wind slabs on top of it in others. This MIN report from Nak Peak on Thursday depicts snow conditions changing with elevation.
In the north, upper elevations are extensively wind affected. A widespread surface crust exists below 1600 m.
A melt-freeze crust from early December is found around 200 cm deep in the snowpack. This crust may have sugary faceted grains sitting above it. This persistent weak layer is most prevalent northwest of Pemberton where large avalanches have failed on this interface recently. This interface doesn’t seem to be a concern in the South (Coquihalla) and little information is known for the North Cascades or far south in Manning Park.
Terrain and Travel
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
- Conditions may have improved, but be mindful that deep instabilities are still present.
Problems
Wind Slabs
Previous wind has deposited recent snow into deeper slabs on leeward slopes at upper elevations. It remains a possibility for isolated wind slabs to react to human triggers.
Cornices have grown large, saggy and fragile.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A problematic layer consisting of sugary faceted grains over a crust may be found around 200 cm deep. The likelihood of triggering an avalanche at this interface has reduced, but the consequence of doing so remains high.
This problem is most prominent along the northwestern border of the region and nonexistent in the south.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 18th, 2021 4:00PM
