Avalanche Forecast
Issued: Dec 19th, 2019 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
Another 20 to 40 cm of snow and strong wind is forecast for Thursday night into Friday. This will continue to load a buried weak layer and may trigger a natural avalanche cycle. Best to avoid avalanche terrain on Friday and give the snowpack time to stabilize.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain.
Weather Forecast
THURSDAY NIGHT: Cloudy with heavy snowfall, accumulation 20 to 40 cm, strong southwest wind, alpine temperature -4 C, freezing level 1200 m.
FRIDAY: Cloudy with snowfall, accumulation 5 to 10 cm, moderate to strong southwest wind, alpine temperature -5 C, freezing level 1100 m.
SATURDAY: Cloudy with snowfall, accumulation 5 to 10 cm, moderate southwest wind, alpine temperature -6 C, freezing level 900 m.
SUNDAY: Cloudy with snowfall, accumulation 10 to 15 cm, light south wind, alpine temperature -6 C, freezing level 900 m.
Avalanche Summary
Numerous large slab avalanches were triggered naturally and by explosives on Thursday. The avalanches failed in the recent storm snow and some of them stepped down to the mid-November weak layer described in the Snowpack Summary.
A natural avalanche cycle may occur Thursday night during the brunt of the storm. Both natural and human-triggered avalanches are expected to be very likely to occur on Friday, failing both in the storm snow as well as the mid-November weak layer.
Snowpack Summary
Another 20 to 40 cm of snow is expected to fall Thursday night, which will add to the 20 to 30 cm that fell on Wednesday and Thursday. All of this snow overlies a weak layer of surface hoar as well as sugary faceted grains and hard melt-freeze crust buried mid-November, which is a recipe for large and destructive avalanches. A natural avalanche cycle may occur Thursday night as this weak layer gets loaded. Skier triggering will be very likely to occur on Friday.
This weak and touchy snowpack is highly atypical for the region and may persist for some time. Conservative terrain travel along with periods of avoidance will be imperative to manage your risk until the weak snow gains strength. Read this informative Mountain Conditions Report for more information.
Problems
Storm Slabs
A natural avalanche cycle may occur Thursday night during the peak of the storm. Human-triggered avalanches are very likely to occur on Friday. Give this new snow some time to bond to underlying layers before venturing into avalanche terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A touchy weak layer is buried in the lower half of the snowpack. This layer has been responsible for many large avalanches and is expected to become more reactive with the snowfall. This is an atypical snowpack for the region, which will require diligence until it strengthens. Avoidance of avalanche terrain is recommended for Friday, as many large and destructive avalanches may occur on this layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 20th, 2019 5:00PM
