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Avalanche Forecast

Archived

Dec 17th, 2019–Dec 18th, 2019

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

Regions

Northwest Inland.

Keep an eye out for reactive deposits of snow in the alpine and around ridges and leeward features.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Tuesday Night: Cloudy with isolated flurries. Alpine temperature -3 C. Southwest wind 30 gusting to 90 km/hr.

Wednesday: Cloudy with scattered flurries, 5-10 cm. Alpine temperature -4 C. South wind 25-35 km/hr.

Thursday: Cloudy and scattered flurries, trace to 10 cm. Alpine temperature -5 C. South wind 20-40 km/hr.

Friday: Cloudy and scattered flurries, trace to 10 cm. Alpine temperature -5 C. South wind 20 gusting to 60 km/hr.

Avalanche Summary

There have been limited field observations and no recent avalanche reports for this region. However, a natural avalanche cycle to size 2.5 occurred Tuesday in the neighboring Northwest Coastal region. This area received higher precipitation amounts (30-60 cm), but similarities in the storm suggest a potential for human triggered storm/wind slabs in the Northwest Inland region as well.

Snowpack Summary

Snowfall blanketed 15-25 cm snow around the region. The new snow likely covered a weak layer of surface hoar and/or a crust on south-southwest aspects. Strong south-southwesterly winds have redistributed new snow and encouraged slab development, especially around ridge features and into the alpine. 

Reports suggest there are 2 burried layers of surface hoar in the upper snowpack - one down 15-25 cm below the new snow, and another down 25-40 cm below older, recent snow.

In leeward terrain, a crust is buried 40-60 cm, and may include surface hoar in sheltered openings up to treeline. Where wind has scoured the snowpack, this crust is at or near the surface.

Older crusts can be found deeper in the snowpack and are generally breaking down and bonding. Snowpack depths are 50-100 cm in alpine areas around Smithers, with depths diminishing rapidly below 1500 m. The relatively thin snowpack has likely caused weak faceted snow to form near the ground.

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.