Avalanche Forecast
Issued: Jan 9th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
bchristie,
Avalanche Canada
Continually check snowpack conditions as you travel through terrain. Back off if you find dense, slabby snow, or signs of instability like shooting cracks. Avoid exposure to terrain traps, especially in steep features.
Summary
Confidence
Weather Forecast
SUNDAY NIGHT: Mostly clear. No new snow expected. Light southwest wind trending to strong at higher elevations. Treeline high around -7 C. Freezing level at valley bottom, with a possible temperature inversion pushing the temperature above 2000 m warmer than -5 C.
MONDAY: Mostly clear, with increasing cloud through the day. Possible trace of snow expected. Moderate southwest winds trending to strong at higher elevations. Freezing level rising to around 500 m.
TUESDAY: Mostly cloudy. 0-5 cm of snow expected overnight, with another 2-5 cm through the day. Moderate to strong southwest wind trending to extreme at higher elevations. Possibly above 100 km/h. Freezing level rising to around 800 m.
WEDNESDAY: Overcast. 5-20 cm of snow expected overnight, with another 10-40 cm through the day. Moderate southwest wind trending to extreme at higher elevations. Freezing level rising to around 1300m.
Avalanche Summary
On Sunday, avalanche control with explosives in the north end of the region produced several storm slab avalanches, mostly small, some large. These avalanches occurred mostly on northeast aspects at treeline and in the alpine.
Friday through Saturday, numerous natural and rider triggered storm slab avalanches up to size 3 were reported by professional operations in the region. Avalanche control with explosives produced size 1.5 to 3.5 avalanches, mostly in the storm snow.
The persistent early December crust/facet layer has recently been active in this region. On Friday, three naturally triggered size 2-3 avalanches on this layer were reported in mountain ranges just west of the Columbia river. They were reported at treeline and above on south and east aspects. Some were known to be windslab avalanches that stepped down to this deeper, persistent layer in a thin, rocky area.
Snowpack Summary
The region received 35 to 50 cm low-density snow and significant periods of strong southerly wind since the start of the storm Thursday. This new snow fell on a variety of surfaces, thin sun crust on solar aspects, isolated surface hoar at treeline on sheltered slopes, fresh wind slabs in lee alpine features at treeline and above or even previous storm snow (20-50 cm) from the last weekend's storm.
We're actively monitoring the early December crust. In some places, it's scoured and on the surface, while in wind-loaded terrain features it can be found as deep as 150 cm below the surface. It consists of faceted grains above a bulletproof crust formed by the Atmospheric Rivers of early December. Avalanches failing on this interface have the potential to be very large.
Terrain and Travel
- If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
- Avoid terrain traps such as gullies and cliffs where the consequence of any avalanche could be serious.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Since Wednesday night, the region has seen 30-40 cm of low density snow along with periods of 50 km/h southerly wind. During the storm, slabs developed in areas with the most rapid loading, but other areas may see new slabs form as the low density snow settles and temperatures warm up.
You may also find the potential for loose dry avalanches in sheltered areas, and wind slabs in lee terrain near mountain tops.
If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
The early December crust can be found down 90 to 150 cm below the surface, with weak, sugary crystals (facets) on top of it.
There were natural avalanches on this layer during the most recent storm, see the avalanche summary for more details.
Sorry for sounding like a broken record, but triggering this layer is a low-probability, high consequence scenario. Even though the avalanche hazard has decreased, a problem like this makes me hesitant to ride a big or committing feature.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 10th, 2022 4:00PM
