Avalanche Forecast
Issued: Dec 20th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
trettie,
Avalanche Canada
Use extra caution at treeline where triggering a persistent slab avalanche is more likely. Make conservative decisions, even a small accident can have big consequences during periods of cold weather and short days.
Summary
Confidence
Moderate
Avalanche Summary
On Monday several natural storm slab avalanches up to size 2 were observed on northeast aspects in the alpine.
Persistent slab avalanche activity has continued to taper off but these layers will likely remain triggerable in specific terrain features.
Snowpack Summary
In the alpine moderate northwest winds have likely redistributed the recent low-density snow (up to 35 cm) and formed fresh wind slabs in immediate lee features. On steep solar slopes, these new wind slabs and fresh snow will be sitting on a thin sun crust. In more sheltered areas, the new snow covers surface hoar and facets.
Around 50cm overlies a layer of surface hoar at treeline and a thin crust on steep south facing slopes. This layer was formed in early December and is less widespread than the other layers of concern in the snowpack.
The mid-November layer consisting of facets and surface hoar is now buried around 80 cm deep. These depths will vary throughout our region with decreased depths in the northern areas.
The snowpack in the forecast region is quite variable and increasingly complex with snowpack depths at treeline varying from 100cm to 200cm.
Weather Summary
Tuesday Night
Flurries bringing up to 5cm of new snow with Moderate southwest winds shifting to light northwest by the morning. Low of -32 at 1800m.
Wednesday
Mostly sunny with no new snow expected. Light to moderate northeast winds and a high of -28 at 1800m.
Thursday
Mostly sunny with no new snow expected. Light variable winds and a high of -28 at 1800m.
Friday
Cloudy with trace amounts of new snow expected. Southwest winds increasing throughout the day. High of -25 at 1800m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Closely monitor how the new snow is bonding to the old surface.
- Avoid open slopes and convex rolls at and below treeline where weak layers may be preserved.
- In times of uncertainty conservative terrain choices are our best defense.
Problems
Persistent Slabs
Two concerning persistent weak layers can be found in the top meter of the snowpack. The first is a surface hoar/crust layer from early December and the second is a surface hoar, facet or crust layer from mid November. The most recent activity on these layers has been in the northern part of the forecast region. These layers are most concerning on sheltered treeline features where surface hoar is most likely to be preserved.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Northwest winds could have formed wind slab on south and east aspects at treeline and above. On south facing terrain these wind slabs could sit over a thin sun crust. In sheltered terrain at treeline wind slabs could sit on a layer of surface hoar. Triggering a wind slab over surface hoar or a crust could result in a larger avalanche.
Be aware that wind slab avalanches could step down to deeper layers.
Aspects: North East, East, South East, South, South West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 21st, 2022 4:00PM
