Avalanche Forecast
Issued: Apr 12th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
jsmith,
Avalanche Canada
Wind slabs may remain reactive to human triggers on lee aspects at treeline and above.
Watch for recently formed and reactive wind slabs as you transition into wind affected terrain.
Summary
Confidence
Moderate
Avalanche Summary
We are still waiting on observations from the weekend's storm. We are expecting a natural storm slab cycle to have run during the peak of the storm and we wouldn't be surprised to see evidence of large, persistent avalanches as the weather clears.
In the White Pass area on Saturday, a rider triggered a cornice fall from a distance, which produced a size 3 persistent slab avalanche on a northeast aspect at 1750 m. The avalanche was 200 cm deep and was suspected of having failed on a layer of facets above a crust buried in January.
Observations are limited at this time of year, please consider sharing any information or photos you have on the Mountain Information Network to help guide our forecasts.
Snowpack Summary
30-40 cm of recent snow has likely seen some redistribution by southerly winds, forming deep deposits in leeward terrain features. The new snow sits over previously wind-affected snow on north and east-facing slopes and a crust on windward south-facing slopes.
A weak layer of surface hoar/crust/facets buried in early January is now buried well over 1 m deep. This layer has produced recent avalanche activity in the White Pass region and remains a concern in terrain where the snowpack is thin. The lower snowpack consists of basal facets, particularly in shallow areas.
Weather Summary
Wednesday night
Cloudy with isolated flurries; 0-5 cm / 20 km/h south ridgetop wind / Temperature at treeline around -8 C
Thursday
Mix of sun and cloud / 10 km/h south ridgetop wind / Temperature at treeline around -7 C
Friday
Mix of sun and cloud / 20 km/h east ridgetop wind / Temperature at treeline around -7 C
Saturday
Cloudy with flurries; 3-10 cm / 30 km/h southeast ridgetop wind / Temperature at treeline around -7 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.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
- Cornice failure may trigger large avalanches.
Problems
Wind Slabs
Wind slabs may remain reactive to human triggers on lee aspects at treeline and above.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer of facets sitting on a crust buried in January has recently been reactive in the White Pass area. Triggering is most likely in areas where the snowpack is thin and weak, or with a heavy load like a cornice fall or the weight of a smaller avalanche in motion triggering this deeper layer.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 13th, 2023 4:00PM
