Avalanche Forecast
Issued: Jan 29th, 2020 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
Watch for newly formed wind slabs in the alpine and open areas at treeline. Take advantage of the good riding in wind sheltered areas below treeline before the big warm-up arrives on Friday.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
Wednesday night: Clear skies. Moderate west to southwest wind. Alpine low -10 C. Freezing level dropping to 500 m.
Thursday: Mix of sun and cloud with starting flurries in the afternoon. Southwest wind becoming strong, extreme at ridgetop. Alpine high -4 C. Freezing level 500 m rising to 1200 m.
Friday: 10-20 mm water equivalent in precipitation starting as snow, turning to rain below 1800 m. Strong southwest wind, extreme at ridgetop. Alpine high +2 C. Freezing level rising from 1500 to 2100 m.
Saturday: 10-30 mm rain overnight below 1500 m. During the day, up to 10 mm water equivalent in precipitation will start as rain, turning to snow as freezing levels drop. Moderate northwest to southwest winds. Freezing level dropping from 1800 m Saturday morning to valley bottom by Sunday morning.
Avalanche Summary
Reports of very large (size 3) deep persistent avalanches have been steadily coming in over the past week from the north half of the region. The most recent events occurred on Monday near Goldbridge, Whitecap and Duffey Lake. While most of these events have been naturals on north to east aspects in the alpine, some have been remotely triggered by skiers.
Natural wind slab avalanches size 2-2.5 were observed on wind-loaded slopes in the alpine on Sunday through Tuesday.
Snowpack Summary
30-60 cm sits over the Jan 20 crust below 2000 m. At upper elevations, the recent snow has been redistributed into wind slabs by strong winds.
Two weak layer of note are isolated to the north half of the region, including the Duffey and Hurley areas. 1) A surface hoar layer is buried 1 m deep in sheltered areas around treeline. 2) A weak basal facet crust complex has been the failure plane in ongoing reports of deep persistent avalanches.The south of the region, including the Coquihalla and Manning areas, currently have no concerns about deep weak layers.
Terrain and Travel
- Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
- Be especially cautious as you transition into wind affected terrain.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Problems
Wind Slabs
Light to moderate snowfall amounts, accompanied by strong winds, will form fresh wind slabs in lee features at alpine and treeline elevations.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Ongoing loading by snowfall and wind has overwhelmed deep weak layers at the bottom of the snowpack. Reports of very large (size 3) deep persistent avalanches have been steadily coming in over the past week from the north half of the region. Avalanches on these layers are most likely to be human triggered from areas of shallow snow cover near rocky outcroppings. These layers do not pose an avalanche problem in the south half of the region.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 30th, 2020 5:00PM
