Avalanche Forecast
Issued: Feb 18th, 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
Heavy snowfall, strong winds, and warm temperatures are a recipe for dangerous avalanches conditions. Expect to find touchy storm slabs, particularly in wind-loaded terrain.
If you see less than 25 cm of new snow, treat the avalanche danger as considerable.
Summary
Confidence
Weather Forecast
A strong pacific system will impact the region on Friday evening, bringing moderate to heavy precipitation and strong winds. Active weather will continue into the weekend, with a clearing trend forecast for early next week.
Friday Overnight: Mixed precipitation, 5-20 cm of new snow accumulation at higher elevations. Freezing level around 1500 m. Moderate to strong southwesterly winds.
Saturday: Continued snowfall, 5-20 cm of accumulation. Freezing level around 1000 m. Moderate to strong southwesterly winds.
Sunday: A mix of sun and cloud, light snowfall. Freezing level dropping to valley bottom with alpine temperatures around -10 C. Light northwesterly winds.
Monday: Mainly clear. Alpine temperatures plummeting into the -20s. Light northeasterly winds.
Avalanche Summary
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.
On Wednesday, several wind slabs and storm slab avalanches were reported up to size 2. These failed in the recent storm snow and didn't step down to deeper layers.
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
Continued snowfall throughout Saturday will add to 15-40 cm of recent storm snow above the old 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. With new load testing the snowpack, this is on our radar. Reports suggest that the surface hoar is most prominent in sheltered openings at and below treeline. Terrain features to be suspect of includes the lee side of protected ridges, openings in the trees, cut blocks, and burns. It is possible that new snow loading and warming may wake this weak layer up, initiating surprisingly large avalanches.
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
The new storm snow will bond poorly to the underlying old snow surfaces. Storm slabs will 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 19th, 2022 4:00PM
