Avalanche Forecast
Issued: Feb 22nd, 2022 3:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
jcoulter,
Avalanche Canada
Recent northeast winds have cause reverse loading and built slabs in unexpected features. Watch for pockets of wind slab on various aspects in exposed terrain and around ridge lines.
Summary
Confidence
Weather Forecast
TUESDAY NIGHT: Clear with moderate northeast winds. Alpine lows of -22.
WEDNESDAY: Sunny with increasing cloud late in the day, winds easing to light from the northwest. Alpine high of -11.
THURSDAY: Mix of sun and cloud, light northerly winds and alpine high of -7.
FRIDAY: Partly cloudy, light northwest wind and high of -8.
Avalanche Summary
On Monday there were several size 1-1.5 wind slabs triggered by skiers as well as a few natural wind slabs spotted in the backcountry. There was also a size 2 avalanche that was triggered remotely by someone walking on a ridge top, that failed on a surface hoar layer buried in late January. A Mountain Information Network post also reported a cornice failure that triggered a small slab.
Snowpack Summary
Recent northeast winds have be scouring and wind affecting open areas and forming wind slabs in lee terrain. This reverse loading means there may be wind slabs in unusual locations. In sheltered locations there is likely around 20-40 cm of snow over an old February drought layer interface that consists of various melt-freeze crusts and old wind-pressed snow depending on your elevation and aspect.
Two layers of buried surface hoar sit in the upper snowpack, most likely to be found and triggered in sheltered areas at treeline. These are now down around 30-50 cm and 60-80 cm deep. Though improving, these layers remain reactive in some snowpack tests and have been responsible for sporadic avalanches, including a size 2 triggered remotely from a skier walking on a ridge top yesterday.
The lower snowpack is well consolidated, with a crust/facet layer found 100 to 200 cm deep. It is currently considered dormant, but could become active later this season. Check out the forecaster blog for more information.
Terrain and Travel
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Problems
Wind Slabs
Watch for pockets of wind slab on various aspects in exposed terrain and around ridgelines. The storm initially came in with southwest winds, but with the intrusion of arctic air, winds switched to the northeast building slabs in less common locations.
These slabs may have formed on top of old crusts and hard wind-pressed snow and there is uncertainty about how quickly they will bond to old surfaces.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Persistent slab avalanches are possible on shaded aspects due to two buried layers of surface hoar. Various combinations of crusts above and below these layers has made the distribution and sensitivity of this problem spotty.
Be cautious on steep open slopes at treeline and below, especially in those sheltered spots where surface hoar is more likely to be preserved.
Aspects: North, North East, East, North West.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Feb 23rd, 2022 3:00PM
