Avalanche Forecast
Issued: Apr 21st, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Cornices.
mconlan,
Avalanche Canada
A spring diurnal pattern dominates. Wind slabs may exist up high. Danger may increase during the heat of the day.
Summary
Confidence
Weather Forecast
WEDNESDAY NIGHT: Cloudy with snowfall, accumulation 5 to 15 cm and locally more with convective flurries, 40 km/h north wind, alpine temperature rapidly dropping from 0 C to -12 C.
THURSDAY: Morning clouds and afternoon clear skies, 20 km/h north wind, alpine temperature -10 C, freezing level 1000 m.
FRIDAY: Mix of sun and cloud, 20 km/h west wind, alpine temperature -7 C, freezing level 1500 m.
SATURDAY: Mix of sun and cloud, 20 km/h northeast wind, alpine temperature -9 C, freezing level 1200 m.
Avalanche Summary
Avalanche activity has quieted down since the heat wave last weekend. Large loose wet and wet slab avalanches were observed during daytime warming but no new avalanches were observed on Tuesday.
Looking forward, spring-like diurnal conditions are forecast to dominate after Wednesday night's storm. Wind slabs could form during the storm and they may be relatively easy to trigger, as they are likely going to overly a hard melt-freeze crust.
Snowpack Summary
Around 5 to 15 cm of snow is forecast to accumulate by Thursday morning. The snow is expected to fall with strong northerly wind, forming small but potentially touchy wind slabs in exposed terrain features at higher elevations. This snow will overly a hard melt-freeze crust to the mountain tops from recent warm air and sunny skies. The snow may moisten during the heat of the day, particularly on sun-exposed slopes and on all aspects below the freezing level.
A weak basal snowpack is found in many parts of the region, including along the eastern slopes of the Rockies like Core Lodge, Wolverine, Bullmoose, Upper Burnt and perhaps around Mt. Robson. In general, steep, rocky slopes with a shallow or thin to thick snowpack are most suspect and should be avoided.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Wind slabs may be poorly bonded to the underlying crust.
- Avoid travelling on slopes below cornices.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
Problems
Wind Slabs
New wind slabs may be found in exposed terrain features. The snow may not bond well, as it will likely sit on a hard melt-freeze crust. Use caution as you enter steep, wind-loaded terrain features.
Aspects: East, South East, South, South West, West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Cornices
Cornices are large and will weaken with daytime warming. Stay well back from them on ridges and avoid travelling beneath them. A cornice fall has the potential of triggering slabs on the slopes below.
Aspects: North, North East, East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 23rd, 2021 4:00PM
