Avalanche Forecast
Issued: Feb 21st, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
rbuhler,
Avalanche Canada
A widespread storm slab problem is expected in the south of the region. Strong northeast wind on Tuesday may increase the reactivity of this recent snow in exposed terrain.
In the north of the region, thin wind slabs should be expected on all aspects in exposed terrain.
Summary
Confidence
Weather Forecast
Arctic high pressure brings a couple more days of cold conditions before returning to seasonal temperatures by Thursday.
Monday Night: Mainly clear, moderate to strong NE wind, treeline low around -20 °C.
Tuesday: Sunny, moderate to strong NE wind, treeline high around -12 °C.
Wednesday: Becoming mainly cloudy in the afternoon, moderate NW wind, treeline high around -10 °C.
Thursday: Sunny, light to moderate N wind, treeline high around -6 °C.
Avalanche Summary
On Sunday in the Coquihalla, a skier-triggered storm slab was reported on a SE aspect at treeline which had a slab depth varying between 20 and 55 cm. The MIN report includes a great photo showing the type of avalanches we continue to expect in the south of the region as ongoing wind continues to redistribute the weekend storm snow. A natural size 2 storm slab was also reported on a SW aspect at 1850 m as well as a variety of small natural and human-triggered loose dry avalanches from steep slopes.
On Sunday in the north of the region, a very small persistent slab avalanche was reported as part of a larger snowpack settlement which occurred at valley bottom near a creek. This failed on the late-January surface hoar down around 40 cm. This suggests that in the isolated areas where large surface hoar is still preserved, the interface may still capable of producing avalanches.
Snowpack Summary
Weekend storm totals were highly variable across the region with around 5-10 cm in the north, 30-40 cm around the Coquihalla, and potentially as much as 60 cm in Allison Pass. During the storm, the wind was blowing from the southwest but has now switched to a northeast direction and wind loading is expected on all aspects in exposed terrain.
20-70 cm now sits above the mid-February crust. The melt-freeze crust is reported to exist on all aspects and elevations, except for high elevation polar aspects in the north of the region. Facets and surface hoar can be found above the crust in the north of the region.
The late-January crust/facet/surface hoar interface is buried down 40-100cm. This layer was most reactive between 1700 m and 2000 m in the north of the region. While this layer now appears to be dormant through most of the region, it may still be possible to trigger it at upper treeline or lower alpine features on polar aspects with a large load like a cornice or in shallow snowpack areas.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Closely monitor how the new snow is bonding to the crust.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Problems
Storm Slabs
In the south of the region, 40-60 cm of recent storm is expected to be most reactive in wind loaded terrain but a widespread storm slab problem likely exists. This snow may be poorly bonded to the underlying crust.
In the north of the region, shifting wind directions means thin wind slabs should be expected on all aspects in exposed terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
The late-January weak layer is down 40 to 100cm and was most reactive between 1700 and 2000 m in the north of the region. It is now likely dormant in most areas, especially where there is a supportive crust above.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 22nd, 2022 4:00PM
