Wind Slabs
N
NE
E
SE
S
SW
W
NW
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely - Very Likely
- Size
- 1–2
Light to moderate snowfall amounts, accompanied by strong winds, will form fresh wind slabs in lee features at alpine and treeline elevations.
Avalanche forecast
View on mapSouth Coast Inland
Jan 29 – 30, 2020Avalanche Canada
Archived · expired 7 years ago
Avalanche danger
Fri
Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
Highlights
New snow and strong winds will form reactive windslabs on Wednesday. The new load will continue to stress deep weak layers which have been producing very large avalanches recently in the north half of the region.
Avalanche problems
Deep Persistent Slabs
NNEESESSWWNW- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible - Likely
- Size
- 2–3.5
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 between 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.
Confidence
Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region.
Weather Forecast
Tuesday night: Mostly cloudy. Alpine low -3 C. Southwest winds building to strong. Freezing level 1200 m.
Wednesday: 10-20 cm new snow. Alpine high -2 C. Strong southwest wind, approaching extreme at ridgetop. Freezing level 1400 m.
Thursday: Mix of sun and cloud with flurries in the evening. Alpine high -2 C. Light to moderate southwest wind. Freezing level 500 m rising to 1900 m in the evening.
Friday: Mix of sun and cloud with flurries in the evening. Alpine high +2 C. Moderate to strong southwest wind. Freezing level 2000 m.
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 and Whitecap. 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.
Snowpack Summary
30-60 cm sits over the Jan 20 crust below 2000 m. At upper elevations, the recent snow has been redistributed by strong southwest 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, have no concerns about deep weak layers.
Terrain and Travel
- Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
- Wind slabs are most reactive during their formation.
- Avoid freshly wind loaded terrain features.
- 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.