Avalanche Forecast
Issued: Feb 3rd, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
astclair,
Avalanche Canada
Avalanche hazard exists where the wind has loaded cornices and drifted recent snow into wind slabs. Give cornices a wide berth and assess for wind slab conditions before committing to terrain.
Summary
Confidence
Weather Forecast
Monday night: Clear, light northwest winds, alpine high temperature -18 C.
Tuesday: Increasing cloud, 5-15 cm of snow, strong southwest winds, alpine high temperature -10 C.
Wednesday: Cloudy, 10-20 cm of snow, moderate southwest winds with strong gusts, alpine high temperature -7 C, freezing level rising to 900 m.
Thursday: Cloudy, isolated flurries, light west winds, alpine high temperature -5 C.
Avalanche Summary
During the storm, numerous small to very large (size 1.5-4) avalanches released naturally in the new snow. These avalanches primarily occurred on leeward aspects at treeline and alpine elevations. Below tree line, wet loose avalanches were releasing naturally during the warm temperatures on Friday.
With continuous stormy weather over the past week, operators have reported three persistent slab avalanches that were both naturally and skier-remote triggered. These very large (size 2.5-4) avalanches were breaking 100-200 cm deep across a variety of aspects above 1900 m. Wind slab avalanches or cornice fall may have the potential to step-down to this layer.
Snowpack Summary
There have been substantial changes to the snowpack over the past few days. 40-60 cm of snow fell during the weekend storm above 1700 m. Higher snow totals fell in the southeastern parts of the region. Strong winds originating from the southwest and shifting to the northwest have created a tricky loading pattern near and above tree line and have elevated concern for cornice triggers. These winds have drifted the snow into stiff slabs on leeward terrain features that remain prone to human triggering. Check out this MIN report for a helpful illustration of these conditions.
During a warming event Saturday night, rain saturated snow surfaces up to around 1700 m that have since formed a crust.
The mid and lower snowpack are generally well settled and strong, however there is a weak layer of surface hoar currently buried 70 to 150 cm deep. This layer has shown signs of instability in the region on slopes between 1700-2400 m. New snow, rain, and warming have added considerable strain to this weak layer, and it may require more time to adjust to the recent load.
Terrain and Travel
- Stay off recently wind loaded slopes until they have had a chance to stabilize.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Wind Slabs
Winds have drifted the recent storm snow into slabs on leeward features that may be possible to trigger. Winds have shifted from southwest to northwest, creating a tricky loading pattern. Areas where wind slabs have formed overlap with areas where cornices may be reaching their breaking point.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of buried surface hoar may persist deeper in the snowpack in the southwest of the region. Easier-to-trigger wind slab avalanches could potentially step down to this persistent slab problem resulting in a very large avalanches.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Feb 4th, 2020 5:00PM
