Avalanche Forecast
Issued: Mar 25th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
JSmith,
Avalanche Canada
Small wind slabs below ridgetops are currently the primary concern.
Summary
Confidence
Low - Uncertainty is due to the limited number of field observations.
Weather Forecast
WEDNESDAY NIGHT: Mostly clear, light west winds, alpine low -12 C, freezing level valley bottom.
THURSDAY: Mix of sun and cloud, light to moderate west winds, alpine high -3 C, freezing level 1500 m.
FRIDAY: Cloudy with isolated flurries; 0-3 cm, light west winds, alpine high -1 C, freezing level 1600 m.
SATURDAY: Cloudy with possible flurries; 0-3 cm, light to moderate southwest winds, alpine high 1 C, freezing level 1700 m.
Avalanche Summary
Over the past week, avalanche activity was reported as natural loose wet avalanches (size 1-2.5) running in steep, sun-exposed terrain. One large (size 2.5) cornice failed as a result of explosive mitigation.
Last week there was a report of a skier remotely triggering (from a distance) a large (size 2) deep persistent slab avalanche at 2600 m on a northwest aspect. The avalanche was triggered from a thin spot, released 40-80 cm deep, and ran on depth hoar near the base of the snowpack.
Snowpack Summary
Sunday's storm only produced a few cm of snow with light to moderate wind mainly out of the southwest.Â
The recent snow sits on a variety of snow surfaces, consisting of sun crusts, hard wind-affected snow, and soft faceted snow. There have also been reports of surface hoar forming on sheltered, shady slopes. See this MIN for a helpful illustration from nearby Glacier National Park. It will be important to track the depth, cohesiveness, and bond of the new snow to these various old snow surfaces across aspects and elevations where you are travelling.
Cornices are large and looming. Surface hoar buried February 22 may be found 50-100 cm deep. Avalanche activity on this layer was last reported March 11th.Â
Deeply buried facets lurk near the bottom of the snowpack. This layer has been responsible for sporadic deep persistent slab avalanches, usually triggered from shallow, rocky start zones.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
- Make observations and assess conditions continually as you travel.
- Be alert to conditions that change with aspect and elevation.
- Cornice failure may trigger large avalanches.
Problems
Wind Slabs
Recent winds may have formed reactive slabs on lee features below ridgetops.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine.
Likelihood
Expected Size
Deep Persistent Slabs
Weak faceted snow near the base of the snowpack continues to be a concern. Treat wind-scoured, rocky, shallow terrain as suspect and avoid big alpine slopes that are threatened by cornices overhead.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 26th, 2020 5:00PM
