Avalanche Forecast
Issued: Jan 8th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
MBender,
Avalanche Canada
Heightened avalanche conditions exist on wind loaded slopes and steep rocky terrain. Although the likelihood of triggering deeply buried weak weak layers is reducing, the consequences of doing so are high.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Friday Night: Mainly cloudy, light west wind, alpine high -7 C, freezing level at valley bottom.
Saturday: Isolated flurries, moderate southwest wind, alpine high -5, freezing level 500 m.
Sunday: Isolated flurries, moderate southwest wind, alpine high -5, freezing level 500 m.
Monday: Flurries, moderate southwest wind, alpine high -2, freezing level 1000 m.
Avalanche Summary
Reports on Wednesday and Thursday indicate several explosives triggered size 2 storm slab avalanches on northerly and southerly aspects at treeline and in the alpine. There was also a report of a size 2 storm slab avalanche that was triggered by another smaller avalanche running nearby. This was at 1950 m on a northeast aspect. As well on Thursday there was a report of 3 explosives triggered size 2.5-3 persistent slab avalanches on north through southwest aspects at 2100 m.Â
A naturally triggered size 3 deep persistent slab avalanche running on a southeast aspect at 2200 m was reported in the Rossland range. It was suspected to have run on Tuesday or Wednesday.
On Tuesday there was a report of a naturally triggered size 2.5-3 wind slab avalanche which stepped down mid-path to the early December persistent weak layer. This was on an east aspect near ridgetop and occurred in the central part of the region.Â
A remotely triggered (from a distance) size 2 persistent slab avalanche was reported near Rossland on Sunday. The details can be seen in MIN posts here and here.
Snowpack Summary
Recent new snow from earlier in the week has been redistributed by southwest wind at upper elevations. In sheltered areas, recent new snow may sit over surface hoar.
Two weak layers are buried in close proximity to one another. They are 70-100 cm deep around Nelson and 50-80 cm deep around Rossland and other western parts of the region. The layers are composed of feathery surface hoar and sugary faceted grains and they overlie a hard melt-freeze crust.Â
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Be especially cautious as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Wind Slabs
Wind slabs may remain sensitive to human triggers, especially in freshly wind loaded features at upper elevations.
Aspects: North, North East, East, North West.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Weak surface hoar and/or faceted grains sit above a melt-freeze crust 70 to 100 cm deep. This layer has been steadily stressed as new snow slowly piled up over the past week. The likelihood of triggering a persistent slab has reduced, but the consequences of doing so remain high.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 9th, 2021 4:00PM
