Avalanche Forecast
Issued: Dec 7th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Loose Wet and Deep Persistent Slabs.
dsaly,
Avalanche Canada
Rain and wet flurries, wind, and high freezing levels - expect to find changing conditions as you gain elevation and transition above the rain/snow line.
Summary
Confidence
Moderate - Uncertainty is due to rapidly fluctuating freezing levels.
Weather Forecast
MONDAY NIGHT: Rain and wet snow, 5-15 cm / Moderate, gusty southwest ridgetop wind / alpine low temperature -1 / Freezing level 2000 m
TUESDAY: Wet flurries and showers, trace to 5 cm / Moderate, gusty southwest ridgetop wind / alpine high temperature +1 / Freezing level dropping to 1500 m
WEDNESDAY: Isolated flurries, trace to 10 cm / Light southwest ridgetop wind / alpine high temperature -3 / Freezing level 1000 m
THURSDAY: Mostly cloudy / Light southwest ridgetop wind / alpine high temperature -4 / 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
Rain and warm temperatures produced moist snow to 1800 m. Above the rain/snow line, Wind is impacting 5-10 cm new snow accumulated by Monday afternoon.
Prior to the storm, a melt-freeze crust covered most surfaces. A variety of wind affected surfaces covered more northerly, alpine terrain. Large surface hoar growth was observed around treeline, but this may have been destroyed by this wet and warm storm. Â
The lower snowpack is characterized by a few crusts that formed during warm periods in November.Â
- 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. We have a lot of uncertainty on the reactivity of this layer - we're keeping it on our radar because we don't have enough information. Recent snowpack tests in the Cayoosh zone found this layer present and down 60 cm, and unreactive to snowpack tests.Â
- In the south of the region, treeline snowpack depth sits around 120-190 cm. 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 fresh storm slabs building throughout the day.
- Be alert to conditions that change with elevation and wind exposure.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
Problems
Storm Slabs
5-10 cm new snow accumulated Monday with more forecasted through the night. Snow and wind will build slabs at upper treeline and alpine elevations. The most reactive slabs will be in wind-loaded areas or around ridges and convex rolls. Be wary of cornices, they may grow quickly under the current conditions.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Loose Wet
At elevations that receive rain (instead of snow) and above 0 temperatures, a wet loose hazard will persist as long as the snowpack is moist or wet.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
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. 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. Be wary of overhead hazards, a large impact (like a cornice failure - see avalanche summary) could trigger the slope below. Keep in mind 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
Expected Size
Valid until: Dec 8th, 2020 4:00PM
