Avalanche Forecast
Issued: Dec 15th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
swerner,
Avalanche Canada
Another storm hits the region and storm slabs will likely be reactive, they may step down to deeper weak layers initiating large to very large avalanches. Avoid avalanche terrain during periods of heavy loading from new snow and strong winds.
Summary
Confidence
Weather Forecast
An active weather pattern hits the region with fast-moving frontal systems bringing snow and strong wind through the forecast period.
Overnight Tuesday: Snow up to 25 cm with a strong southwest wind. Freezing level 700 m.
Wednesday: Another 10-25 cm of snow. Moderate and gusty southwest wind. Freezing level 800 m.
Thursday: Cloudy. Light snow 5 cm. Strong southwest wind.
Friday: Snow 20-30 cm. Strong southwest wind and freezing level 800 m.
Avalanche Summary
No new reports on Tuesday at the time of publishing.
On Monday, a few naturally-triggered Icefall events up to size 2 were reported from Bear Pass. Loose-dry sluffing up to size 1 was seen from steep and rocky terrain features. The last deep persistent slab avalanches released on December 11 in the north of the region near Ningunsaw.
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 will see substantial snowfall amounts Tuesday night and into Wednesday, especially to the south of the region as well as strong southwest wind. Expect storm slabs to build during the storm, 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 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
- Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
- Watch for fresh storm slabs building throughout the day.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.
Problems
Storm Slabs
Snow is expected to accumulate over the day with an associated strong southwest wind. Heavy snow is forecast in the far south with substantially less accumulation in the northern half of the region.
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
Valid until: Dec 16th, 2020 4:00PM
