Avalanche Forecast
Issued: Dec 12th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet and Wind Slabs.
zryan,
Avalanche Canada
The potential for a temperature inversion and sun on Tuesday means loose wet avalanches may occur on steep slopes. Be alert to changes in aspect, elevation, and time of day.
Pockets of wind slabs may exist at higher elevations near ridges and peaks that are further away from the coast where the storm snow was deep, and dry, and will take more time to settle and gain strength.
Summary
Confidence
Moderate
Avalanche Summary
During the storm on Friday and Saturday, numerous small (size 1) natural and human-triggered storm slab avalanches were reported in the North Shore mountains. These avalanches occurred at treeline and below treeline on a variety of aspects.
Natural activity tapered on Sunday, but a report of a skier-triggered wind slab confirmed that human triggering remained possible. This avalanche occurred on a wind-loaded northwest-facing slope in the alpine. See MIN report here (Thanks for sharing!)
If an alpine temperature inversion develops on Tuesday, wet loose avalanches may occur on steep solar.
Keep sharing your observations via the MIN; it helps strengthen our information gathering.
Snowpack Summary
Upper snowpack: Last week's storm snow totals around 50 to 70 cm. This storm arrived warm and mixed with rain near the coast (e.g. North Shore Mountains) and a crust may now exist near the surface. This new snow is sitting on a sun crust on steep, solar aspects and feathery surface hoar crystals in isolated sheltered and shaded areas. Mid-pack: softer, weaker layers of less cohesive snow around 80 - 100 cm down should be gaining strength as they squish. Lower-pack: a thick melt-freeze crust and increasing strength.
At 1000 m the snowpack depth is around 150 cm. In many areas, below treeline elevations are still below the threshold for avalanches.
Weather Summary
Monday night
Clear. Alpine temperatures drop to a low of -3 °C. Ridge wind light to 20 km/h from the north. Freezing level drops to 200 metres.
Tuesday
A mix of sun and cloud. Alpine temperatures reach a high of 1 °C. Ridge wind light to 15 km/h from the northwest. Freezing level rising to 2300 metres.
WednesdaySunny. Alpine temperatures reach a high of 1 °C. Mostly light ridge wind occasionally gusting to 30 km/h from the northwest. Freezing level rising to 1500 metres.
ThursdaySunny. Alpine temperatures reach a high of 6 °C. Mostly light ridge wind occasionally gusting to 50 km/h from the north. Freezing level rising to 2000 metres.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
- Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.
Problems
Loose Wet
Wet loose avalanches may occur if warm temperatures and sun weaken the upper snowpack.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Strong southerly winds during last week's storm have created deep deposits of wind slab near ridges and peaks. These slabs are most likely to be an issue inland from the coast, where the storm snow was deep, dry, and will take more time to settle and gain strength.
Aspects: North, North East, East, South West, West, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 13th, 2022 4:00PM
