Avalanche Forecast
Issued: Dec 18th, 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.
kdevine,
Avalanche Canada
Continued stormy weather with heavy snow and strong winds will keep avalanche danger elevated. Avoid avalanche terrain.
Summary
Confidence
Weather Forecast
FRIDAY NIGHT - Mainly cloudy with flurries, 5 cm / southwest wind, 40-60 km/h / alpine low temperature near -4
SATURDAY - Snow, 10-20 cm / southwest wind, 80-100 km/h / alpine high temperature near -2 / freezing level 1000 m
SUNDAY - Flurries, 5-10 cm / southwest wind, 30-60 km/h / alpine high temperature near -3
MONDAY - Cloudy with sunny periods and isolated flurries / light winds / alpine high temperature near -5
Avalanche Summary
Widespread natural avalanches are expected with the continuing stormy weather.
There were a few explosives triggered size 2 storm slab avalanches reported on Thursday.
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Snowpack Summary
The Northwest Coast has been getting hit by wave after wave of intense precipitation. There has been upwards of 80 cm of new snow this week. With another 10-20 cm in the forecast for Saturday, storm slabs will continue to be reactive.
This new snow sits on previously wind-affected snow at higher elevations, potentially a layer of surface hoar in sheltered areas, and a crust at lower elevations. Initially, the storm snow will likely have a poor bond to these old snow surfaces.
A crust that was buried in early December is now down 80-100 cm in the alpine but is closer to the surface at and below treeline elevations.
The early-November crust is buried around 100-200 cm at treeline. This crust may have weak and sugary facets above it in parts of the region. This layer has produced large, full-depth avalanches in the past few 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
- Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.
- 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.
- The more the snow feels like a slurpy, the more likely loose wet avalanches will become.
Problems
Storm Slabs
Recent and ongoing storm snow with strong southwest winds has formed 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 19th, 2020 4:00PM
