Avalanche Forecast
Regions: South Coast Inland.
Expect to find widespread human triggerable storm slabs in the Coquihalla and Allison Lake zones Monday as north wind forms 20 to 40 cm of storm snow into reactive slabs. The best riding will be found in wind sheltered terrain.
Confidence
Moderate - Forecast precipitation (either snow or rain) amounts are uncertain. Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.
Weather Forecast
SUNDAY NIGHT: Freezing level at valley bottom, 5 to 10 cm of snow, north wind picking up overnight with enough speed to form fresh slabs.
MONDAY: Broken cloud cover, no new snow expected, moderate north wind, daytime high temperature at 1500 m around -10 C.
TUESDAY: Broken cloud cover, no new snow expected, moderate north/northeast wind, daytime high temperature at 1500 m around -15 C.
WEDNESDAY: Scattered cloud cover, no new snow expected, light variable wind, daytime high temperature at 1500 m warming slightly to -8 C.
Avalanche Summary
We suspect that rider triggerable storm and wind slabs will be found throughout the region on Monday.
No new avalanche activity to report from Saturday.
On Friday one skier controlled size one wind slab avalanche was reported in the south of the region. This avalanche ran on the mid February crust.
Snowpack Summary
By Monday morning, storm totals from the weekend should be around 5 to 10 cm in the north, 20 to 30 cm around the Coquihalla, and potentially as much as 40 cm in Allison Pass. Moderate north wind Sunday night into Monday is expected to form fresh storm slabs.
20 to 50 cm 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.Â
The late-January crust/facet/surface hoar interface is buried down 40 to 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 in many parts of the region it may be possible to trigger with a heavy load or in shallow snowpack areas at upper treeline and lower alpine features on north aspects.
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.
Avalanche Problems
Storm Slabs
While not expected to be much of an issue in the north, expect potentially deep and reactive wind fueled storm slabs in the Coquihalla and Allison Pass zones Monday.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1.5 - 2.5
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: Unlikely
Expected Size: 2 - 3