Avalanche Forecast
Issued: Feb 27th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
jcoulter,
Avalanche Canada
Don't let incremental loading, southwest winds and rising freezing levels catch you off guard.
It is time to take a step back from bigger objectives.
Summary
Confidence
Weather Forecast
Snowfall amounts may vary widely in the region and by forecast model.
Sunday Night: Light snow 5 cm possible, moderate to strong southwest wind, low of -7 °C.
Monday: Light snowfall 5-15 cm, moderate to strong southwest wind, treeline high around -1 °C.
Monday night/Tuesday: Snowfall 10-20cm, moderate to strong SW wind, freezing levels reaching around 2000 m.
Wednesday: Light flurries, moderate southwest wind, treeline high around zero.
Avalanche Summary
On Saturday a group accidentally triggered a size 2 wind slab carrying, but not burying a rider. Also on Saturday a size 1.5 cornice fall was reported, but it didn't trigger any slabs on the slopes below. A MIN from the Purcell Wilderness Conservancy found variable ski conditions, but no signs of instability.
On Friday a skier controlled size 2 wind slab was reported on a south east aspect over a crust. Explosives control also took out some cornices that triggered some slabs below. One other small avalanche was triggered on a sheltered roll at treeline which failed on the mid-February surface hoar.
On Thursday, a few natural wind slabs up to size 2.5 were observed in the alpine in the western part of the region. Explosive use triggered several size 2-2.5 cornice releases. One of these cornices releases triggered a small slab on the slope below.
Snowpack Summary
The new snow will bury a highly variable snow surface which includes wind-affected surface in exposed terrain, a thin sun crust on solar aspects which may be faceting, surface hoar in sheltered areas, and/or old storm snow which may be faceting on shaded slopes.
A weak interface from mid-February was down around 20-40 cm prior to the storm. It consists of a sun crust on solar aspects, facets, and/or surface hoar. This layer was previously only reactive in wind-loaded terrain where a slab had formed but it is expected to become a more widespread problem as the storm progresses and builds a more widespread slab.
A layer of buried surface hoar from late-January sits 30-60 cm deep in the snowpack and is most likely to be found on north aspects in sheltered areas. Though there haven't been reports of recent avalanches on this layer in this region, it is still on the radar of many operations and could potentially wake up during the storm.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Be alert to conditions that change throughout the day.
Problems
Wind Slabs
Watch for new wind slab formation in lee terrain on Sunday as new snow starts to accumulate with southwest wind. In parts of the region with higher snowfall amounts, this may present more as a storm slab problem on all aspects.
Lingering old wind slabs from the recent northeast wind may still be reactive to human-triggering in exposed high elevation terrain. These would be most likely where they overlie a weak layer from mid-February.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 28th, 2022 4:00PM
