Avalanche Forecast
Issued: Jan 13th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Persistent Slabs and Loose Wet.
swerner,
Avalanche Canada
Storm slabs will remain reactive, especially where they sit above a persistent weak layer. Don't let the sunshine and fresh snow lure you into aggressive terrain, use a conservative approach and avoid overhead hazards. The danger rating in the South (Coquihalla) is a step lower.
Summary
Confidence
Moderate - Uncertainty is due to rapidly fluctuating freezing levels. Uncertainty is due to the extreme variability of wind effect on the snowpack.
Weather Forecast
An upper ridge will build Thursday will bring dryer and sunnier conditions. Freezing levels may spike to 2300 m by the afternoon on the Coquihalla and 1300 m on the Duffy and North.
Thursday: A mix of sun and cloud and freezing levels rising through the day to 2300 m. Ridgetop wind up to 60Km/hr from the southwest.
Friday: Cloudy with light snow amounts (5-10 cm). Gusty ridgetop wind from the West and freezing levels near 1300 m.
Saturday: Cloudy with some flurries. Light West wind and freezing levels 1100 m.Â
Avalanche Summary
No new reports came in at the time of publishing this forecast. I suspect a natural avalanche cycle occurred on overnight Tuesday and Wednesday, especially in the Northern part of the region where the precipitation fell as snow.
On Wednesday, the Southern part of the region saw widespread natural avalanche activity up to size 3. Most of the avalanches reported were wet loose and glide slabs. In the North minor sluffing in steep terrain at treeline and below was reported. No alpine observations to note due to the weather.Â
Snowpack Summary
Up to 50 cm of new snow accompanied by strong wind fell throughout the region. Most of this came as snow in the North and rain in the South. New and reactive storm and wind slabs will likely exist at upper elevations, especially in sheltered areas where the new snow may overlie the recently buried surface hoar. Lower elevation terrain may see a firm crust as temperatures drop.
A melt-freeze crust from early December is found around 100 to 200 cm deep in the snowpack. This crust may have surface hoar or sugary faceted grains sitting above it. This persistent weak layer is most prevalent in the North (e.g., Duffey Lake, Hurley) and large avalanches have failed on this interface in the past week. 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 aware of the potential for large avalanches due to the presence of buried weak layers.
- Make conservative terrain choices and avoid overhead hazard.
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- Watch for unstable snow on specific terrain features, especially when the snow is moist or wet.
Problems
Storm Slabs
New and reactive storm and wind slabs are expected to linger after the storm. Strong southwest wind will persist depositing recent snow into deeper slabs on leeward slopes in the alpine. Cornices may have grown large and fragile. They deserve respect and a wide berth from below and above.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A couple of problematic layers may be found around 100 to 200 cm deep. The layers are primarily in the north of the region (e.g. Duffey, Hurley) and include weak layers of surface hoar and faceted grains above a hard melt-freeze crust. The likelihood of triggering a persistent slab has reduced, but the consequence of doing so remains high.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Loose Wet
Freezing levels are expected to rise to 2300 m on the Coquihalla and 1900 m in the Duffy Lake area by the afternoon. If the warm temperatures break down the crust expect loose wet avalanches to occur, especially from steeper terrain features and solar aspects.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Jan 14th, 2021 4:00PM
