Avalanche Forecast
Issued: Dec 27th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Persistent Slabs and Storm 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.
Watch for wind effect in recent storm snow. Expect wind loading around ridgelines and in mid slope terrain features.
Deeper weak layers remain a concern for step down avalanches in wind loaded terrain.
Summary
Confidence
Avalanche Summary
On Monday a widespread natural avalanche cycle occurred with numerous small to large ( size 1-2) avalanches occurring. These avalanche primarily failed on surface hoar that was buried in the middle of December as well on the persistent weak layer buried mid November.
An increase in avalanche activity was reported during Sunday. Explosive testing at two different operations triggered many avalanches, all within the previous storm snow on north aspect terrain in the alpine. These avalanches where small to large (size 1 and 2) . Crown depths ranged from 20 to 40 cm and ran from 50 m in length to 150 m.
Additionally, professional snowmobile operations reported remotely triggering 8 small (size 1) avalanches during travel . These avalanche were located on south aspect terrain at 1600 m elevation , depths were approx. 30 cm with run lengths every short 3 m.
Activity from Friday was limited to small loose dry avalanches in steep terrain features.
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 20cm of storm snow, creating wind slabs on north and east facing terrain features. Wind slabs sit over hard wind affected surfaces, a layer of facets or surface hoar increasing reactivity.
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. Triggering becomes more likely as temperatures rise.
Alpine snowpack distribution is variable, with depths ranging from 70 to 140 cm.
Weather Summary
Tuesday Night
Cloudy with light snowfall 1 to 4 cm. Moderate southwest winds 30 km/h. Freezing levels variable between 1000 and 1500 m. Alpine temperatures cooling to -5°C .
Wednesday
Cloudy with light snowfall 1 to 5 cm. Moderate southwest winds 40 km/h. Freezing levels remain around 700 m with alpine temperatures of -4°C.
Thursday
Mostly cloudy some mid day clearing expected, very light snowfall, trace amounts. Light southwest winds 15 km/h. Freezing levels remain below 500 m with alpine highs of -3°C.
Friday
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.
Problems
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
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 a layer of surface hoar buried in the middle of December.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 28th, 2022 4:00PM
