Avalanche Forecast
Regions: East Island, North Island, South Island, Vancouver Island, West Island.
Use careful routefinding to work around areas of wind-loaded snow. The weak layer under our storm snow produced large avalanches during the storm and could still react to a human trigger.
Confidence
Moderate
Avalanche Summary
On Sunday, a sledder accidentally triggered a size 2.5 wind slab avalanche on a west aspect at 1580 m on Mt Beadnell, commonly referred to as the Adrian riding area. This resulted in a critical burial, serious injuries, and helicopter evacuation.
There is some uncertainty around how much longer the interface below our massive storm snow will persist as a weak layer. Smaller wind slabs formed with new snow are meanwhile likely to trigger and may produce step-down avalanches.
Snowpack Summary
Around 20 cm of new snow overnight Monday brought 4 - day storm totals to 80 to 150 cm. Strong southerly ridgetop winds have been creating variable surfaces in exposed areas and built deep deposits in lee features at alpine and treeline.
The new snow sits over a layer of softer, faceted snow which itself overlies a crust on all but high north aspects. Large surface hoar grains have been observed just below the storm snow in the Mt Cain area. The bond at this interface is likely improving under the weight of the recent snow but it is not yet reliable. It has produced recent destructive avalanches.
The mid and lower snowpack is generally settled and strong.
Below 1000m the upper snowpack may be moist or wet.
Weather Summary
Tuesday night
Clearing but staying mainly cloudy. 20 to 30 km/h southwest ridgetop wind. Freezing level to 600 m.
Wednesday
Partly cloudy. 10 to 15 km/h southwest ridgetop wind. Treeline high around -1 °C with freezing level to 1300 m.
Thursday
A mix of sun and cloud. 15 to 20 km/h variable ridgetop wind shifting northwest. Treeline high around +5 °C with freezing level shooting to 3300m.
Friday
Mainly sunny. 10-15 km/h north ridgetop wind. Treeline high around +14 °C with freezing level to 3500 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- 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.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
Avalanche Problems
Wind Slabs
New snow from Monday has created surface wind slabs and storm slabs above a thick layer of storm snow that doesn't yet have a reliable bond with the interface it buried last week. Surface avalanches may step down to this layer.
Aspects: North, North East, East, South East, North West.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 2
Persistent Slabs
80-150 cm of recent storm snow is settling over a weak layer of faceted snow and spotty surface hoar on a firm crust. This combination produced large, destructive avalanches on the weekend and needs time to stabilize.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1.5 - 3
Loose Wet
Bouts of sunshine could quickly initiate wet loose avalanche activity on Wednesday.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 1 - 2