Avalanche Forecast
Issued: Dec 5th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
dsaly,
Avalanche Canada
As you transition from melt-freeze conditions to dry snow, be on the lookout for wind-loaded pockets in lee features. And the possibility of wet loose avalanches will persist where snow is moist or wet.
Summary
Confidence
Weather Forecast
SATURDAY NIGHT: Increasing clouds / Moderate, southwest ridgetop wind / alpine low temperature -8 / Freezing level dropping gradually to 1000 m.
SUNDAY: Cloudy and wet flurries, up to 5 cm / Moderate to strong, southwest ridgetop wind / alpine high temperature +1 / Freezing level 1500 m.
MONDAY: Wet snow, 10-20 cm. / Strong, southwest ridgetop wind / alpine high temperature 0 / Freezing level rising to 2000 m.
TUESDAY: Snow and rain, 10-20 cm. / Moderate, gusty southwest ridgetop wind / alpine high temperature +1 / Freezing level 2000 m.
Avalanche Summary
No new avalanche observations submitted on Thursday or Friday.
On Wednesday, the northern part of the region, several natural avalanches were reported up to size 2 with some older ones from the previous storm up to size 2.5. A couple of isolated natural glide crack avalanches up to size 1.5 were also reported. In the southern half, numerous natural wet loose avalanches occurred up to size 2 mostly from southerly aspects.
Last Tuesday, 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
Recent sun and warm air well into the alpine had the greatest impact on the upper snowpack, melt freeze conditions exist on most aspects and elevations. Where dry snow prevails, such as shaded alpine and upper treeline slopes, wind slabs have developed on leeward terrain.
Large surface hoar growth has been reported slopes sheltered from the warm temperatures, sunshine and wind.
The lower snowpack is characterized by a few crusts that formed during warm periods over the last month.
- In the north, treeline snowpack depth sits around 80 to 120 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, the snow line has been reported around 700 m near Hope, and treeline snowpack depth sits around 80-150 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
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- 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
Wind Slabs
At upper elevations where snow dry snow prevails, winds have redistributed dry snow forming pockets of wind slabs in lee features and below ridgelines. Expect new slabs to develop as the incoming storm brings flurries and more wind.
Aspects: North, North East, East, North West.
Elevations: Alpine, 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. Be wary of overhead hazards, a large impact (like a cornice failure) could trigger the slope below. There's a lot of uncertainty on the reactivity of this layer, however 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 6th, 2020 4:00PM
