Avalanche Forecast
Issued: Jan 25th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Loose Wet and Wind Slabs.
rgoddard,
Avalanche Canada
With the rise in temperatures expect to see signs of instability like pinwheeling and tree bombs.
This could create smaller accumulated loading on the surface and trigger weak layers buried further down creating large avalanches.
Choose terrain that won't expose you to the consequences.
Summary
Confidence
Avalanche Summary
No new avalanches were reported in our region for the last two days.
Sunday's avalanche activity in the region consisted mainly of small (size 1 or less) dry loose releases from steeper terrain with skier traffic and ski cutting. For our neighbours to the north, several wind slab and persistent slab avalanches were reported that ranged in size from one to two.
Although persistent and deep persistent avalanches have been on the decline, warming that is expected to arrive on Thursday brings real concern for the potential for natural as well as human triggering of weak layers buried deeper in the snowpack.
Snowpack Summary
New snow, 10 to 20 cm has buried a new weak layer. It consists of faceted snow, surface hoar (3 to 10 mm), and a crust. The surface hoar is found in sheltered areas up to 2200 m and the crust is present on steep solar aspects. Variable winds at high elevations have pushed this new snow around, creating wind slabs on a variety of aspects.
A freezing rain or rime crust buried on January 18 now sits about 15 to 30 cm deep. More layers of concern (crusts, facets, and surface hoar) can be found in the upper snowpack between 30 to 50 cm down. They have yet to produce avalanche activity but they are something to keep an eye on.
Our main layers of concern include a surface hoar layer developed in early January, down roughly 50-70 cm, and a melt-freeze crust from late December that is now down approximately 70-90 cm. These layers are responsible for our persistent slab problem.
Our deep persistent slab problem stems from a weak layer created in mid-November and it is now buried 100 to 190 cm deep. These layers are a major concern and can produce large or even very large avalanches with human or machine triggers.
Weather Summary
Wednesday Night
Mostly clear with increasing clouds, no accumulation, winds west northwest 15 km/h gusting to 35, treeline temps around 0 C.
Thursday
Cloudy with possible late day sun, up to 9 cm accumulation focused mostly in the western area of our region, winds west 15 km/h gusting to 45, treeline temperatures getting to above 0 C due to a temperature inversion and freezing levels up to 700 m.
Friday
A mix of sun and cloud, up to 7 cm accumulation in some parts of the region ending in the morning, winds northwest 25 km/h, treeline temperatures around -5 C.
Saturday
A mix of sun and cloud, up to 4 cm accumulation, winds northeast 15 to 30 km/h, treeline temperatures -17 C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- 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.
- The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
Problems
Persistent Slabs
A persistent weak layer of surface hoar is buried 50 to 70 cm down. This depth is prime for human triggering. Below treeline this layer may present as a rain crust.
Deeper in the snowpack, near the ground, the snowpack is very weak and can be triggered under the right circumstances. Be especially suspicious of shallow, rocky, or cross-loaded areas with variable snow depths.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Loose Wet
Warm air at higher elevations and potential sun input will affect mostly steep, sun exposed slopes. Wet loose avalanches in motion have potential to trigger weak layers deeper in the snowpack to create larger, more destructive avalanches.
Aspects: South East, South, South West.
Elevations: All elevations.
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 26th, 2023 4:00PM
