Avalanche Forecast
Issued: Mar 18th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
bchristie,
Avalanche Canada
Start on small features, and gather information before choosing your line. Extra caution in sheltered, shaded terrain at treeline. Windslab avalanches are becoming less likely, but they have the potential to be large if they slide on a preserved layer of weak, feathery crystals.
Summary
Confidence
Weather Forecast
FRIDAY NIGHT: Mostly cloudy. 3-5 cm of snow expected (up to 10 cm north of Hazelton) . Moderate to strong south ridgetop winds. Freezing level at valley bottom in the morning, rising to around 1000 m in the afternoon. Alpine low around -8 °C.
SATURDAY: Partly cloudy. Possible trace of snow expected. Light to moderate southwest ridgetop winds. Freezing level at valley bottom in the morning, rising to around 900 m in the afternoon. Alpine high around -7 °C.
SUNDAY: Partly cloudy. 0-5 cm of snow expected. Light to moderate south ridgetop wind, with periods of strong southwest in the high alpine. Freezing level at valley bottom in the morning, rising to around 750 m in the afternoon.
MONDAY: Partly cloudy, decreasing cloudy through the day. Scattered flurries. Moderate to strong southwest ridgetop wind. Freezing level rising to 1500 m.
Avalanche Summary
Most recent avalanche observations are small windslabs, and loose dry in steep terrain.
The layer of weak, feathery, surface hoar crystals that was buried in late February has surprised a few people in the last week. The most active area seems to be north of Hazelton, mostly in terrain that is difficult to get to without a helicopter, but there have been incidents closer to Smithers as well. For example: This MIN report describes a size 2 slab avalanche triggered by a snowmobile on a southeast facing alpine slope from last Saturday.
Most other avalanches on this layer that surprised people:
- Occurred on north or northeast aspects (likely with increased loading due to recent winds).
- Occurred in sparsely treed features between 1200 and 1600m
- Quickly propagated across the whole feature, or were triggered remotely.
Snowpack Summary
15-30 cm of recent snow has been redistributed into by moderate to strong south to southwest winds. This snow is settling over a sun crust on solar aspects, and a temperature crust on all aspects as high as 1700 m. Some operations have reported surface hoar in this layer on sheltered north aspects. Those specific locations could be of more 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.
Terrain and Travel
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- Wind slabs are most reactive during their formation.
- 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 weak layers.
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
Expected Size
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:
- avoid 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
Expected Size
Valid until: Mar 19th, 2022 4:00PM
