Avalanche Forecast
Issued: Dec 28th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Storm Slabs and Wind Slabs.
jpercival,
Avalanche Canada
There is a Special Public Avalanche Warning in effect for this region. Learn more: avalanche.ca/spaw
The new storm snow overlies a layer of surface hoar that is very reactive. Utilize simple terrain and careful route finding if planning mountain travel.
Deeper weak layers remain a concern for step down avalanches in wind loaded terrain.
Summary
Confidence
Moderate
Avalanche Summary
Monday and Tuesday has been very active as a skier controlled, skier accidental combined with a widespread natural avalanche cycle has occurred. This ongoing avalanche cycle produced numerous small to large (size 1-2) avalanches. These avalanche primarily failed on surface hoar that was buried in the middle of December as well stepping down to the persistent weak layer buried mid November. A number of noted avalanches reported occurred in terrain that had been previously heavily compacted, these observations and reports, support an overwhelming sense that the snowpack is currently weak, fragile and unsupportive.
Additionally, a number of these avalanches stepped down to ground as the lower snowpack is faceted weak and unconsolidated.
If you are headed into the backcountry please consider filling out a Mountain Information Network report.
Snowpack Summary
A period of warm and wet weather has moistened upper surfaces with rain reported up to the 2100m elevation.
Sustained light to moderate southwest winds have continued to move up to 40 cm of storm snow, creating wind slabs on north and east facing terrain features. Storm and wind slabs sit over hard wind affected surfaces, and a layer of facets or surface hoar that has been very active over the past 72 hrs.
The main concern is a layer of surface hoar, facets, or crusts buried 40 to 80 cm deep from mid November. Avalanche activity on this layer has tapered off but it could still be possible to trigger this layer in isolated terrain features near treeline.
Alpine snowpack distribution is variable, with depths ranging from 70 to 140 cm.
Weather Summary
Wednesday Night
Cloudy with light snowfall 1 to 2 cm. Moderate southwest winds 30 km/h. Freezing levels descending to valley bottom with alpine temperatures of -9°C.
Thursday
Cloudy some mid day clearing expected, very light snowfall, trace amounts. Light southwest winds 20 km/h. Freezing levels remain below 700 m with alpine highs of -6°C.
Friday
Clearing with no precipitation forecast. Light southwest winds 15 km/h. Freezing levels near 500 m with alpine highs of -7°C.
Saturday
Clearing with no precipitation forecast. Light southwest winds 15 km/h. Freezing levels at valley bottom with alpine highs of -12°C.
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.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Travel in alpine terrain is not recommended.
Problems
Persistent Slabs
A layer of surface hoar, facets and, a crust from mid November is buried around 40-80 cm deep. This layer has become hard to trigger but could still be sensitive to rider traffic on isolated slopes at treeline and below where the snow above feels stiff, slabby and consolidated.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Storm Slabs
This storm slab overlies buried surface hoar and has been very easy to trigger with many natural avalanche occurring.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Southwest winds will likely continue to form wind slabs in exposed terrain at treeline and above. These slabs will be found on east and north facing slopes sitting above facets and surface hoar, increasing reactivity and propagation.
If enough mass is present, wind slab avalanches could step down to deeper layers.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 29th, 2022 4:00PM
