Avalanche Forecast

THURSDAY NIGHT: Mostly cloudy. 0-2 cm of snow expected. Moderate to strong southwest ridgetop winds. Freezing level dropping to near valley bottom. Alpine low around -7 °C.

FRIDAY: Partly cloudy with scattered flurries. Moderate to strong south ridgetop winds, periods of extreme southwest in the high alpine. Freezing level at valley bottom in the morning, rising to around 1000 m in the afternoon. Alpine high around -5 °C

SATURDAY: Partly cloudy with scattered flurries. Light to moderate southwest ridgetop winds. Freezing level at valley bottom in the morning, rising to around 900 m in the afternoon.  

SUNDAY: Mostly sunny, increasing cloud in the afternoon. Possible trace 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.

On Tuesday and Wednesday, natural windslab avalanches up to size 2 were reported, as moderate winds continued to move snow. A couple of large cornice falls were also reported. 

A couple of recent, rider triggered, slab avalanches on the late February surface hoar layer:

• Size 2 Northwest of Hazelton, on a north aspect around treeline. It started on the mid-March surface hoar layer, and it stepped down to the late-February surface hoar layer. 
• Size 1.5 Northeast of Hazelton, on a northeast aspect around treeline. Surprisingly wide avalanche on a small feature.

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: A MIN report describes a size 2 slab avalanche triggered by a snowmobile on a southeast facing alpine slope from Saturday. 

Concerning snowpack test results on this layer have us watching for more activity as fresh snow and wind increase the weight on it. At this time, it is most likely to be triggered where winds are loading sheltered open slopes at treeline. 

15-30 cm of storm snow is being redistributed into wind loaded pockets by moderate to strong southwest winds. This overlies 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 windslabs continue to build.  

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. 

• 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.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.