Avalanche Forecast
Issued: Feb 13th, 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.
mconlan,
Avalanche Canada
Wind slabs will continue to build and be triggerable by riders. Persistent slabs may also linger in specific terrain. Conservative terrain travel is recommended.
Summary
Confidence
Moderate
Avalanche Summary
Riders triggered wind slabs in leeward terrain primarily in upper treeline and alpine elevations over the weekend. Most of these wind slabs likely occurred within the weekend's storm snow.
On Friday, a large avalanche was triggered by riders, likely releasing on the weak layer described in the Snowpack Summary. See this MIN for details and photos, highlighting the propagation potential and high consequence nature of this layer.
Looking forward, strong wind will continue to build new wind slabs in lee terrain features, which will likely remain triggerable by riders in the coming days. It also remains possible that riders could trigger a persistent slab avalanche, where the layer exists.
Snowpack Summary
Strong southwest wind is forecast for Tuesday, which will redistribute the 20 to 30 cm of snow from the weekend and form wind slabs. The snow surface may remain soft in wind-sheltered terrain. This snow overlies old and hard wind slabs in wind-exposed terrain. A hard melt-freeze crust that extends up to about 1700 m is around 50 cm deep.
A weak layer of surface hoar and facets may be buried about 50 to 100 cm deep on north to east aspects in alpine and upper treeline elevations. The layer may rest on a harder melt-freeze crust. Where preserved, this layer has shown to have very high propagation potential and capable of producing large avalanches hundreds of metres wide.
Weather Summary
Monday Night
Mostly cloudy with light snowfall, accumulation 1 to 3 cm, 20 to 30 km/h southwest wind, treeline temperature -11 °C.
Tuesday
Cloudy with light snowfall, accumulation 1 to 3 cm, 40 to 50 km/h southwest wind, treeline temperature -11 °C.
WednesdayCloudy with snowfall then clearing, accumulation 5 cm, 40 to 60 km/h southwest wind, treeline temperature -8 °C.
ThursdayMix of sun and cloud with no precipitation, 30 to 40 km/h southwest wind, treeline temperature -8 °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.
- Wind slabs are most reactive during their formation.
- Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
- The best and safest riding will be on slopes that have soft snow without any slab properties.
Problems
Wind Slabs
Strong southwest wind will form new wind slabs in lee terrain features, which will overly slabs formed on the weekend.
Aspects: North, North East, East, South East, North West.
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 14th, 2023 4:00PM
