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Avalanche Forecast

Archived

Jan 5th, 2022–Jan 6th, 2022

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

Regions

South Coast Inland.

New slabs may form across the region, with the thickest expected in the south of the region (e.g., Coquihalla, Manning).

Confidence

Moderate - Forecast snowfall amounts are uncertain. Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

WEDNESDAY NIGHT: Cloudy with snowfall, accumulation 5 to 15 cm with the most in the south of the region, 20 km/h southwest wind, alpine temperature -12 C.

THURSDAY: Cloudy with snowfall, accumulation 5 to 15 cm with the most in the south of the region, 30 km/h southwest wind, alpine temperature -9 C.

FRIDAY: Cloudy with snowfall, accumulation 10 to 30 cm with the most forecast around Coquihalla and Manning, 30 km/h southwest wind, alpine temperature -8 C.

SATURDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 20 km/h southwest wind, alpine temperature -12 C.

Avalanche Summary

Many naturally-triggered storm slab avalanches were observed on Tuesday and Wednesday. The avalanches were generally small to large (size 1 to 2) and found at all elevation bands.

Looking forward to Thursday, we anticipate that new storm slabs will be triggerable by riders at all elevations and on all aspects in sheltered terrain, and wind slabs in lee terrain features at higher elevations.

Snowpack Summary

Around 20 to 30 cm of snow is forecast for Wednesday night into Thursday, which will likely form new storm slabs in areas sheltered from the wind and wind slabs in exposed terrain. This snow will build on the 50+ cm of snow that has fallen since January 1.

All of this snow overlies various old surfaces that formed during the cold spell in late December. These layers include a melt-freeze crust on sun-exposed aspects, weak and feathery surface hoar in areas sheltered from the wind, weak and sugary faceted grains, and hardened surfaces from strong wind. There is uncertainty in how long it will take for all this snow to bond to these layers.

Around 80 to 200 cm deep, a weak layer of faceted grains may be found above a melt-freeze crust that formed in early December. The layer is most prominent between 1700 and 2100 m. The last observed avalanche on this layer was around December 24, suggesting that this layer has become dormant. The most likely place to trigger it would be in thin, rocky snowpack areas.

The lower snowpack is well-settled and strong.

Terrain and Travel

  • Watch for fresh storm slabs building throughout the day.
  • Choose conservative terrain and watch for clues of instability.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.