Avalanche Forecast
Issued: Jan 4th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
Stormy conditions continue on Sunday, with the most snowfall expected in the south of the region. Travel in avalanche terrain is not recommended. A touchy weak layer in the north of the region requires particular caution.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain.
Weather Forecast
SATURDAY NIGHT: Cloudy with snowfall, accumulation 10 to 20 cm near Coquihalla and 5 to 10 cm elsewhere, moderate to strong southwest wind, alpine temperature -7 C, freezing level 1000 m.
SUNDAY: Cloudy with snowfall, accumulation 20 cm near Coquihalla and 5 to 10 cm elsewhere, moderate to strong southwest wind, alpine temperature -7 C, freezing level 1000 m.
MONDAY: Cloudy with snowfall, accumulation 5 to 10 cm, moderate southwest wind, alpine temperature -7 C, freezing level 600 m.
TUESDAY: Cloudy with snowfall, accumulation 10 to 20 cm, moderate southwest wind, alpine temperature -3 C, freezing level 1300 m.
Avalanche Summary
Many large to very large avalanches were triggered in the region on Friday and Saturday. Some of them released in recent storm snow with crowns of 25 to 80 cm. Many avalanches in the north of the region released on the weak layer of faceted grains described in the snowpack summary. They were 50 to 120 cm thick and released on all aspects between 1800 m and 2300 m.
Snowpack Summary
Intense snowfall continues in the region, forming dangerous avalanche conditions. Snowfall amounts may reach 30 to 40 Saturday night into Sunday near Coquihalla and otherwise 20 cm of snow may accumulate in the region. This snowfall will add to the 30 to 60 cm from Friday. All of this snow is falling with strong southwest wind, redistributing it in exposed terrain. The snow may overly a touchy weak layer of feathery surface hoar, making storm slabs particularly touchy.
A persistent weak layer is present near the bottom of the snowpack in the northern half of the region (e.g., Duffey, Hurley). The weak layer of sugary faceted grains exists around a hard melt-freeze crust from mid-November, which is an indicative snowpack setup for large and destructive avalanches. The likelihood of natural and human-triggered avalanches on this layer remains elevated with the snow and wind loading occurring during this stormy period.
Terrain and Travel
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- Make conservative terrain choices and avoid overhead hazard.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Problems
Storm Slabs
Intense stormy conditions continue, with another 30 to 40 cm of snow possible Saturday night into Sunday around Coquihalla and up to 20 cm for the rest of the region. The snow will fall with strong southwest wind, loading lee terrain features. Touchy storm slabs will be reactive to both human and natural triggers on Sunday.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
In the north half of the region, a touchy weak layer is buried near the bottom of the snowpack. This layer has been responsible for recent large, destructive avalanches. The likelihood of triggering this layer will be elevated during the stormy conditions on Sunday.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 5th, 2020 5:00PM
