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Avalanche Forecast

Archived

Dec 12th, 2022–Dec 13th, 2022

Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast, North Shore, Sasquatch, Sasquatch, Tetrahedron, Harrison-Fraser.

The potential for a temperature inversion and sun on Tuesday means loose 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.

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.

Wednesday

Sunny. 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.

Thursday

Sunny. 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

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.