Avalanche Forecast

Issued: Dec 6th, 2020 4:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs, Loose Wet and Deep Persistent Slabs.

Avalanche Canada dsaly, Avalanche Canada

Email

With new flurries and wind, keep a look out for wind slabs building through the day.

Summary

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

SUNDAY NIGHT: Cloudy and flurries, up to 5 cm / Moderate to strong, southwest ridgetop wind / alpine low temperature -4 / Freezing level 1200 m

MONDAY: Flurries and wet snow, 5-15 cm / Strong, southwest ridgetop wind / alpine high temperature +1 / Freezing level rising to 2000 m

TUESDAY: Flurries, 5-15 cm / Moderate, gusty southwest ridgetop wind / alpine high temperature +1 / Freezing level dropping to 1500 m

WEDNESDAY: Isolated flurries / Light southwest ridgetop wind / alpine high temperature -3 / Freezing level 1000 m

Avalanche Summary

On Saturday, a few wet loose avalanches to size 2 were observed from steep rocky features in the sun. Outside of a few other small wet loose avalanches from steep terrain, there have been no avalanche observations since last Wednesday (Nov 2) when a widespread wet loose avalanche cycle up to size 2 was triggered by warming.

Of note to consider in the Duffy area: A notable avalanche occurred last Tuesday (Nov 1) when a large size 3 natural avalanche was observed on a NE aspect at 2400 m. It was reported as a cornice failure triggering the slope below and appeared to have slid on the early November crust near the base of the snowpack.

Have you been out and about in the mountains? If so please submit to the Mountain Information Network (MIN). It doesn't have to be technical it can be as simple as a photo. Photos are especially helpful! Sending out a big thank you to the already submitted MIN's this season. Thanks everyone!

Snowpack Summary

A melt-freeze crust covers most slopes resulting from recent sun and warm temperatures. Where cold, dry snow prevailed (upper elevations on more shaded and polar slopes), winds continue to press slabs into lee features. Large surface hoar growth has been observed in treeline areas sheltered from the warm temperatures, sunshine and wind.  

The lower snowpack is characterized by a few crusts that formed during warm periods in November. 

  • In the north, treeline snowpack depth sits around 80 to 150 cm. The crust of note here is sitting near the base of the snowpack, likely surrounded by a weak layer of sugary facets. Snowpack tests and recent avalanche activity suggest that this layer could be triggered by humans and produce large avalanches.
  • In the south of the region, treeline snowpack depth sits around 120-190 cm. Melt-freeze snow surfaces exist after the recent warming. The deeper crusts in this area are generally down around 60-80 cm in the alpine and well bonded to surrounding snow.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be alert to conditions that change with elevation and wind exposure.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

Problems

Wind Slabs

An icon showing Wind Slabs

Expect increasing slab development as wind redistributes flurries accumulating throughout the region. The most reactive slabs will be in wind-loaded areas or around ridges and convex rolls.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Loose Wet

An icon showing Loose Wet

As freezing levels spike late Monday (and areas that get rain instead of snow), a wet loose hazard will persist anywhere the snowpack is moist or wet.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

In the north of the region (e.g., Duffey Lake), a weak layer of sugary faceted grains around a hard melt-freeze crust sits near the base of the snowpack. Be wary of overhead hazards, a large impact (like a cornice failure - see avalanche summary) could trigger the slope below. There is a lot of uncertainty on the reactivity of this layer - we're keeping it on our radar because we don't have enough information. And if this layer is triggered, it will likely produce large avalanches. This problem does not exist in the south of the region.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

1.5 - 2.5

Valid until: Dec 7th, 2020 4:00PM

Login