Avalanche Forecast
Issued: Jan 10th, 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.
mconlan,
Avalanche Canada
Heightened avalanche conditions exist on wind-loaded slopes and in steep, rocky terrain. The likelihood of triggering deeply buried weak layers is reducing but the consequence of doing so remains high.
Summary
Confidence
Weather Forecast
SUNDAY NIGHT: Cloudy with isolated flurries, 20 km/h southwest wind, alpine temperature -6 C.
MONDAY: Cloudy with snowfall, accumulation 5 cm, 40 km/h southwest wind, alpine temperature -6 C.
TUESDAY: Cloudy with snowfall, accumulation 10 to 20 cm, 40 km/h southwest wind, alpine temperature -4 C.
WEDNESDAY: Cloudy with snowfall then clearing, accumulation 15 to 25 cm, 30 km/h west wind, alpine temperature -5 C.
Avalanche Summary
A few small wind slab avalanches were triggered by riders on Saturday. They occurred on north to northwest aspects and around 2000 m.
Of note, a naturally-triggered size 3 deep persistent slab avalanche released on a southeast aspect at 2200 m in the Rossland range last Tuesday or Wednesday. The avalanche likely failed on the weak layers described in the Snowpack Summary and scrubbed to ground. Persistent slab avalanche activity has quieted in the past few days since this report. Although the likelihood of triggering these layers has reduced, the consequence of doing so remains high.
Snowpack Summary
Lingering wind slabs may be found at higher elevations from strong southwest wind. In sheltered areas, recent new snow may overlie surface hoar.
Two weak layers are buried in close proximity to one another. They are 70 to 100 cm deep around Nelson and 50 to 80 cm deep around Rossland and other western parts of the region. The layers are composed of surface hoar and faceted grains and they overlie a hard melt-freeze crust. Many MIN reports describe these layers and their snowpack test results. The results suggest that it remains possible for riders to trigger these layers.
Another layer of faceted grains above a melt-freeze crust that formed in early November is upwards of 200 cm below the surface. This has been the suspected failure layer of a few very large avalanches that released last week in the Rossland range.
Terrain and Travel
- Be careful as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
- Cornice failure may trigger large avalanches.
Problems
Wind Slabs
Riders may still trigger wind slabs due to snow transportation from recent southwest wind. The most suspect terrain features are wind-loaded pockets at higher elevations.
Aspects: North, North East, East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Weak surface hoar and/or faceted grains sit above a melt-freeze crust around 70 to 100 cm deep. The likelihood of triggering a persistent slab has reduced, but the consequence of doing so remains high.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 11th, 2021 4:00PM
