Avalanche Forecast
Issued: Jan 21st, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Deep Persistent Slabs and Wind Slabs.
rgoddard,
Avalanche Canada
Large to very large avalanches continue to be produced from our complex snowpack.
Don't let today's sun lull you into compromising terrain.
Seek out low-angle terrain that has a deep snowpack.
Summary
Confidence
Moderate
Avalanche Summary
Avalanche control work done on Friday produced very large (up to size 3.5) avalanches. These were from our persistent problem and deep persistent problem. Under the right circumstances, riders can trigger these layers. Heavier loads like those created by smaller avalanches will trigger these deeper layers as well.
Snowpack Summary
In exposed areas, northerly winds have been redistributing 10 to 15 cm of new snow, likely creating small wind slabs in a reverse loading pattern. In many areas the new snow accumulated on a thin rime or freezing rain crust that formed in the region on Jan 18, a new layer of concern for us to watch over the near term.
Including the new snow, about 30 to 40 cm has been settling and bonding to an older mix of wind-affected and sheltered lower-density storm snow above about 1700 m and to a rain crust from mid-January at lower elevations.
A more problematic layer of weak surface hoar from early January now sits preserved 50 to 70 cm deep, especially prevalent in sheltered terrain at the treeline. This layer has been identified as the failure plane in many recent avalanches in the region and remains reactive in snowpack tests.
Another problematic layer composed of a facet/crust combination is down 60 to 90 cm (and 2 to 10 cm thick at treeline elevation). Below this, the mid-pack is settled and consolidated.
A concerning and weak layer of facets and crust 20 to 50 cm thick make up the basal snowpack.
Check out an awesome state of the snowpack video update HERE.
Weather Summary
Saturday Night
Cloudy, snow tapering off during the night with 3 cm accumulation, 35 km/h southwest wind, temperatures -8 C at 1500 m.
Sunday
Sunny, no accumulation, 40 km/h northwest winds, temperatures around -8 C at 1500 m.
Monday
A mix of sun and cloud with clouds easing towards the end of the day, no accumulation, 30 km/h west winds with gusts to 50, temperatures around -5 C at treeline.
Tuesday
Sunny with cloudy periods, no accumulation, 15 km/h west wind gusting to 50, temperatures -5 C at 1500 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
Problems
Persistent Slabs
A persistent weak layer of surface hoar responsible for many recent avalanches exists 50-70 cm deep in the snowpack - prime depth for human triggering large, destructive avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
Weak, faceted grains make up the basal snowpack. Where supportive to riders, a melt-freeze crust may be providing a bridging effect, making it more difficult to trigger deeper layers. Be especially suspicious of shallow, rocky, or cross-loaded areas with variable snow depths.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Shifting winds have been acting on 10 to 15 cm of loose snow sitting on a freezing rain or rime crust, likely forming small wind slabs on a wide range of aspects in exposed areas. Southwest winds has and will continue to be the primary factor here.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 22nd, 2023 4:00PM
