Avalanche Forecast
Regions: Northwest Inland.
Watch for wind slabs at upper elevations and keep in mind a recently buried weak layer remains triggerable around treeline.
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Sunday night: Cloudy. Up to 5 cm new snow. Moderate southwest wind. Alpine low around-5 °C.
Monday: Cloudy with flurries bringing a trace. Moderate southwest wind. Alpine high around -2 °C. Freezing level rising to 1500 m.Â
Tuesday: Snowfall 10-20 cm. Strong southwest wind. Alpine high around -1 °C. Freezing level 1700 m.Â
Tuesday: Snowfall 5-15 cm. Moderate southwest wind. Alpine high around -6 °C. Freezing level 1000 m.Â
Avalanche Summary
Most recent avalanche observations have been small wind slabs, and loose dry in steep terrain.
Persistent slab avalanches on a weak layer of surface hoar crystals buried in late February have surprised a few people in the last week with quickly propagating accidental and remote triggers. The layer has been most active on north-northeast aspects between 1200 and 1600 m in areas north of Hazelton.
Snowpack Summary
15-30 cm of recent snow has been redistributed into wind slabs in wind exposed terrain. This snow sits over a crust on solar aspects and below 1700 m. Some operations have reported surface hoar in this layer on sheltered north aspects. Those specific locations could be of increasing concern as the load of snow above them increases.
Around 30-45 cm deep, a surface hoar layer buried in late February is preserved in wind sheltered features at treeline and low alpine elevations. Recent snowpack tests and avalanche observations suggest that weak spots on this layer are hard to find, but the resulting avalanches will be surprisingly large if you trigger them.
The thick mid-February crust is now buried 50-80 cm deep, and in terrain where it is topped by a layer of loose, sugary facets, it could be possible to trigger with very large loads such as avalanches in motion or cornice falls.
The lower snowpack is well protected by the mid-February crust, and triggering avalanches below this layer is unlikely at this time.Â
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Caution around convexities or sharp changes in terrain.
- Be aware of the potential for large avalanches due to the presence of buried weak layers.
Avalanche Problems
Wind Slabs
Use extra caution around ridgecrests, and in cross loaded gully features.
Start on small slopes and gather information before heading into bigger terrain.
Watch and listen for signs of instability, like shooting cracks or whumpfs.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2
Persistent Slabs
In late February, weak, feathery surface hoar crystals were buried. In some places they were sitting on top of a crust. In early March multiple spotty layers of smaller surface hoar crystals were buried.
Avalanche activity on these layers is not consistent across the region, so it's hard to pin down exactly where each one will be a problem. Luckily, the approach to avoiding them is consistent:
- treat convexities as suspect in shaded, sheltered, slopes around treeline.
- use extra caution at ridge crests and on convex rolls.
- knowing the snowpack history in your local area can help you be more confident in your terrain selection, and if you don't know the history, fall back on the first two points.
Aspects: North, North East, East.
Elevations: Treeline.
Likelihood: Unlikely - Possible
Expected Size: 1 - 2