Avalanche Forecast
Issued: Dec 17th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Deep Persistent Slabs and Loose Wet.
swerner,
Avalanche Canada
Storm slabs continue to build and remain reactive through the forecast period. Stick to non-avalanche terrain and avoid overhead avalanche slopes that have the potential to run into treeline terrain.
Summary
Confidence
Low - Forecast snowfall amounts are uncertain. Uncertainty is due to the limited number of field observations.
Weather Forecast
Another strong Pacific frontal system arrives Thursday afternoon bringing moderate to heavy storm snow amounts and strong southwest wind.
Overnight Thursday: Snow 10-20 cm with strong West winds and freezing levels 700 m.
Friday: Snow 20-30 cm with strong southwest wind. Alpine temperatures near -1 and freezing levels 1000-1500 m.
Saturday: Heavy snow up to 30 cm possible. Strong southwest wind and freezing levels near 800 m.
Avalanche Summary
At the time of publishing, there have been no recent avalanche reports for Thursday.
Data in this region is very sparse. Please consider sharing your observations with the Mountain Information Network; even just a photo of your day helps. Thank you to those that have already submitted this winter.
Snowpack Summary
The region has seen up to 50 cm of recent storm snow by Thursday. Expect reactive storm slabs particularly in wind-affected terrain at and above treeline. The snow will fall onto previous wind-affected snow at higher elevations, potentially a layer of surface hoar in sheltered areas, and a crust at lower elevations. Initially, the new storm snow will likely have a poor bond to these old snow surfaces.
The early-December crust is now down 80-100 cm in the alpine but close to the surface at and below treeline elevations.
The early-November crust is buried around 100 to 200 cm at treeline elevations. The early-November crust may have weak and sugary faceted grains above it in parts of the region, which have produced large, full-depth avalanches in the past weeks. Uncertainty remains about where this layer remains a problem in the region, but it may be localized to the northern half of the region.
Terrain and Travel
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.
- The more the snow feels like a slurpy, the more likely loose wet avalanches will become.
Problems
Storm Slabs
Recent storm snow and strong southwest wind have built reactive storm slabs. Large avalanches are expected, especially where they sit above a crust buried in early December.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
Weak faceted grains may overly a melt-freeze crust near the base of the snowpack. There is uncertainty on where this layer remains a problem in the region, but large avalanches have recently occurred in the northern half of the region. The most likely area to trigger it would be in thin, rocky snowpack areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Freezing levels are uncertain for Friday. If you see rain and warming at lower elevations you may see loose wet avalanches, especially from steep terrain features.
Aspects: All aspects.
Elevations: Below Treeline.
Likelihood
Expected Size
Valid until: Dec 18th, 2020 4:00PM
