Avalanche Forecast
Issued: Feb 19th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
zryan,
Avalanche Canada
Storm slabs are expected to remain reactive to human triggering, especially in wind-loaded terrain.
Forecast will be updated at 6:30AM (PST) if overnight snowfall exceeds forecast.
Summary
Confidence
Weather Forecast
Get ready for a wicked 180 as arctic air invades the province bringing cold temperatures and clear skies.
Saturday Overnight: Continued snowfall, trace to 5cm accumulation. Freezing level dropping to valley bottom, alpine temperatures around -10 C. Light to moderate northwesterly winds.
Sunday: Mainly cloudy, light snowfall. Alpine temperatures around -12 C. Light northwesterly winds.
Monday: Mainly clear. Alpine temperatures around -20 C. Light to moderate northeasterly winds.
Tuesday: Mainly clear. Alpine temperatures around -20 C. Light to moderate northeasterly winds.
Avalanche Summary
Human-triggered storm slab avalanches are likely on Sunday.
As the winds picked up on Thursday, operators in the south of the region reported numerous small skier-triggered wind slabs failing easily on the old hard surface.
Last weekend, sledders near Blue River remote triggered several large slab avalanches on shaded aspects at treeline. The failure plane of these avalanches is uncertain, but large remote triggered avalanches would make us suspect it failed on the late January buried surface hoar. Photos from this incident can be seen here.
Snowpack Summary
Saturday's 10-40 cm of new snow will add to this week's snowfall with 30-100 cm now overlying the old, hard surface. This surface is comprised of facetted snow, a melt-freeze crust at lower elevations, a sun-crust on steep solar aspects, and hard wind-affected snow in the alpine and exposed treeline.
Digging deeper in the snowpack another weak interface exists of primarily surface hoar/crust now buried up to 120 cm. There has been no reactivity on this layer in the past week, and test results indicate that this layer is bonding well and trending towards being unreactive.
The lower snowpack is generally strong and well-bonded.
Terrain and Travel
- Use increased caution at all elevations. Storm snow is forming touchy slabs.
- Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
Problems
Storm Slabs
40-100 cm of recent storm snow may bond poorly to the old firm surface. Storm slabs will continue to be reactive, especially on leeward slopes where deeper, and stiffer slabs exist due to wind loading.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A weak layer formed in late January may be found 50 to 120 cm deep in the snowpack. This layer consists of faceted snow, a sun crust on steep solar aspect, and most notably large surface hoar crystals in sheltered terrain.
Reactivity has begun to taper, but a significant amount of new load may cause this layer to 'wake up'.
The most reactivity on this layer has been seen between 1600-2200 m in open areas in the trees, in cut blocks, and on steep convexities.Terrain features to be suspect of include the lee side of ridges, openings in trees, cut blocks, and burns, especially on northerly aspects where the layer may not be capped by a firm crust.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 20th, 2022 4:00PM
