Avalanche Forecast
Issued: Jan 5th, 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
Many large avalanches have occurred in the region. The snowpack will require more time to heal from the recent snow and wind loading. Travel in alpine and treeline avalanche terrain is not recommended until the snowpack shows signs of stabilizing.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
SUNDAY NIGHT: Cloudy with some clearing and isolated flurries, local accumulation 5 to 10 cm, moderate west wind, alpine temperature -10 C, freezing level below valley bottom.
MONDAY: Cloudy with snowfall, accumulation 5 to 10 cm in the north of the region and 10 to 20 cm in the south of the region, moderate southwest wind, alpine temperature -7 C, freezing level rising to 800 m over the day.
TUESDAY: Cloudy with snowfall, accumulation 10 to 30 cm, moderate to strong southwest wind, alpine temperature -3 C, freezing level 1400 m.
WEDNESDAY: Morning snowfall and afternoon clearing, accumulation 5 to 10 cm, light northwest wind, alpine temperature -10 C, freezing level 500 m.
Avalanche Summary
On Sunday, storm slabs were reported as being touchy and having surprisingly wide propagation. They were most touchy on lee slopes at treeline and alpine elevations. Many natural avalanches released within the recent storm snow.
Large persistent slab avalanches continue to be triggered naturally, by humans, and explosives in the northern half of the region. On Saturday, the avalanches were 50 to 70 cm thick and released on all aspects between 1800 m and 2300 m. Some of the avalanches sympathetically triggered other avalanches, suggesting the potential for wide propagation.
Snowpack Summary
Around 50 to 80 cm of recent snow has formed touchy storm slabs in the region, with the thickest slabs found in the southern half of the region. The snow has been 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
- Travel in alpine terrain is not recommended.
- Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
- Be aware of the potential for wide propagation.
- Any steep opening in the trees should be treated as suspect right now.
Problems
Storm Slabs
Many storm slab avalanches have occurred in the region and they have been described as touchy and having the potential to propagate far, particularly where they overly a weak layer of surface hoar. The slabs are likely deepest and touchy in lee terrain features at treeline and alpine elevations and in large openings below treeline. These slabs may take some time to stabilize.
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 remains elevated and the consequence of doing so would be severe.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 6th, 2020 5:00PM
