Avalanche Forecast
Issued: Dec 19th, 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.
jcoulter,
Avalanche Canada
If your area receives more than 15-20 cm of new snow through Sunday bump the danger rating by one step. In other areas the snowpack will need time to adjust to recent storm snow and wind loading so conservative terrain selection is still recommended.
Summary
Confidence
Moderate - Uncertainties in both the snowpack structure and the weather forecast limit our confidence.
Weather Forecast
SATURDAY NIGHT - Flurries 5-10 cm / light southwest wind but strong gusts possible / alpine high temperature near -2 / freezing level 700 m
SUNDAY - Flurries, sunny periods possible, 5-10 cm / light southwest wind gusting to strong / alpine high temperature near -2 / freezing level up to 600 m
MONDAY - Cloudy with sunny periods and isolated flurries / light winds / alpine high temperature near -5Â
TUESDAY - Cloudy with sunny breaks, no new precipitation / light winds / alpine high-4 /temperature inversion possible
Avalanche Summary
On Sunday there were reports of shooting cracks in convex (roll over) type features. Avalanches up to size 2 out of steep, wind loaded features were reported on Saturday.
On Wednesday and Thursday there were many MIN reports suggesting the ever increasing storm snow amounts were reactive to human triggering.
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
Precipitation will start to ease in most areas on Sunday but storm slabs will likely continue to be reactive to human triggering. Some areas have seen upwards of a meter of new snow in the past week.
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 80-120 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
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Storm snow with strong southwest wind have formed reactive storm slabs. Recent snowfall amounts vary widely across 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 20th, 2020 4:00PM
