Avalanche Forecast
Issued: Dec 11th, 2019 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Wind Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
The Monashees along the southern border of the region will see enhanced snowfall amounts compared to the rest of the region. Reactive storm slabs building through the day will elevate the danger rating to Considerable at alpine and treeline in this area.
Summary
Confidence
Weather Forecast
Wednesday Night: Cloudy with flurries starting, accumulating 5-10 cm by morning, concentrated in the southwest of the region. Alpine low -7, light to moderate southwest wind.
Thursday: Periods of snow accumulating 5-15 cm concentrated in the southwest of the region. Alpine high -5, moderate southwest wind gusting strong.
Friday: Flurries accumulating to 5 cm, alpine high -5, light west wind.
Saturday: Mainly cloudy, isolated flurries with trace accumulation, alpine high -5, light northwest wind.
Avalanche Summary
Numerous natural, explosive and skier triggered avalanches size 2-2.5 on a variety of aspects have been reported recently throughout the region and in neighboring Glacier National Park. Some of these avalanches were triggered in areas of shallow snowcover or wind slab and stepped down to the persistent November layer resulting in avalanches large enough to injure or bury a person.
Snowpack Summary
Large, feathery surface hoar crystals have been observed on the snow surface at all elevations throughout the region, and are now covered by a dusting of snow. As new snow falls on this layer over the day Thursday, reactive storm slabs may build in areas of higher snowfall.
Soft wind slab can be found in the lee of features such as ridge tops, ribs and gulleys. Elsewhere, the upper snowpack remains soft and unconsolidated in the cool temperatures.
A weak layer formed in late November is now buried 70-120 cm below the surface. This is the layer of concern relating to the persistent slab avalanche problem. The weak layer may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect. It can most likely be found in areas sheltered from the wind, but open to a view of the sky, such as near treeline. Below this, variety of crusts from late October are buried deeper in the snowpack.
Problems
Storm Slabs
Reactive storm slabs may build over the day Thursday in the Monashees along the southern border of the region, where snowfall amounts are forecast to be around 20 cm. The new snow will fall on large, feathery surface hoar crystals have been observed on the snow surface at all elevations throughout the region. This can be a recipe for remote triggering and wide propagation in the storm snow.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Wind slabs can be found in lees of features such as ridgetops, ribs and gullies. Windslab avalanches have surprised a number of skiers in recent days.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
This weak layer formed in late November may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect. It is buried 70-120 cm below the surface and can most likely be found in areas sheltered from the wind, but open to a view of the sky, such as near treeline.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 12th, 2019 5:00PM
