Avalanche Forecast
Issued: Feb 20th, 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.
zryan,
Avalanche Canada
Seek out wind-sheltered terrain where you can avoid wind slabs and find great riding.
The lingering potential for large persistent slab avalanches is best managed through low-consequence terrain selection and good travel habits.
Summary
Confidence
Avalanche Summary
On Sunday, a size 1 wind slab was skier-triggered in a gully at treeline, reminding us that despite great riding in sheltered areas, reactive wind slabs still exist in more exposed areas. See the full report here.
Last Thursday our field team observed debris from a previous large persistent slab avalanche. At least once a week evidence of large persistent slab avalanches is reported. Keep this in mind when travelling in the backcountry.
Snowpack Summary
Up to 30 cm of recent snowfall remains loose and powdery in sheltered areas. In wind-affected areas, variable winds may have created wind slabs on all aspects. This recent snow sits above a decomposing crust up to 5cm thick that is widespread to 1300 m and can be found up to 1700 m in isolated areas. This crust sits on the surface in wind-exposed terrain and is otherwise buried about 50 to 80 cm in wind-loaded terrain. The crust appears to be bonding to the snowpack.
In alpine and upper treeline elevations, a weak layer of surface hoar and facets may be buried about 80 to 120 cm deep on north-to-east aspects. This layer may rest on a harder melt-freeze crust. Where preserved, this layer is capable of producing large avalanches hundreds of metres wide.
Weather Summary
Monday night
A mix of sun and cloud with a clearing trend, isolated light flurries. Ridgetop winds north 30 km/h with gusts to 50. Alpine temperatures drop to -20ºC.
Tuesday
Partly cloudy. Ridgetop winds north 20-40 km/h. Alpine temperatures rise to -15ºC.
Wednesday
Mainly clear skies. Ridgetop winds north becoming northeast 10-25 km/h. Alpine temperatures rise to -12ºC in the afternoon.
Thursday
Increasing clouds with snow beginning in the evening. Winds switching to southwest 15-30 km/h. Alpine temperatures rise to -10ºC in the afternoon.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
- The best and safest riding will be on slopes that have soft snow without any slab properties.
Problems
Wind Slabs
Variable winds over the past few days have created wind slabs on all aspects in exposed areas. Expect the most recently formed and reactive slabs to be on south-to-west aspects from overnight northerly winds.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
We continue to see periodic avalanches on a weak layer of surface hoar and facets buried about 100 cm deep. Resulting avalanches have propagated for hundreds of metres, with some being remotely triggered from hundreds of metres away. The common trend is that they are on north to east aspects around 1500 to 1700 m in elevation.
Aspects: North, North East, East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Feb 21st, 2023 4:00PM
