Avalanche Canada ahanna, Avalanche Canada

Northwest Coastal Avalanche Forecast

Jan 15th, 2020 4:00PM

Outflow winds may be easing Thursday afternoon but it is still dangerously cold out there right now. Save your toes for more tolerable temperatures and new snowfall this weekend.

Summary

Confidence

Moderate - Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Weather Forecast

Wednesday night: Clear with few clouds. Strong valley outflows with moderate alpine wind from the southeast. Alpine temperatures around -28 C.

Thursday: Mix of sun and cloud with isolated flurries bringing a trace of new snow. Light alpine winds from the south, strong low elevation outflows easing through the day to light. Alpine temperatures around -25 C.

Friday: Mix of sun and cloud. Light south to southeast winds. Alpine temperatures around -20 C.

Saturday: Mostly cloudy with scattered flurries bringing 15-30 cm of new snow. Moderate to strong southeast winds. Alpine temperatures around -18 C.

Avalanche Summary

On Tuesday, explosive control work along the Shames Road corridor produced size 1.5 windslab avalanches, following the natural windslab cycle observed Sunday through Monday morning amid reverse loading by strong outflow winds. Cornice and serac failures have also observed recently, as they typically become brittle in the cold.

Reports of deep persistent slab avalanches have been trickling in over the past week. They are associated with a November crust layer near the base of the snowpack, producing very large avalanches with crown depths of around 2 m. Observations are typically in alpine terrain, on lee or cross-loaded slopes. In one case, the slab was triggered remotely by a vehicle from shallow, rocky terrain, propagating to deeper areas. Among the earliest reports was this MIN from the storm last week.

Snowpack Summary

Extensive wind effect observed at all elevations. North to east aspects in the alpine have been wind scoured, with isolated hard windslab in lees, and notable cornice growth. This wind affected surface snow may overly a layer of surface hoar in many areas, particularly at treeline. In sheltered areas, snow is unconsolidated and well preserved by the cold temperatures.

A deep crust from mid November lurks at the base of the snowpack. A couple of recent large avalanches have run on this layer high in the alpine. 

Terrain and Travel

  • Keep your guard up at lower elevations. Wind slab formation has been extensive.
  • Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

Valid until: Jan 16th, 2020 5:00PM