Avalanche Forecast
Issued: Jan 27th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
rgoddard,
Avalanche Canada
Snowfall amounts will vary throughout the region. Low-density snow will be easily transported by moderate to strong winds.
Be careful as you transition into wind-affected terrain and monitor slab conditions of new snow.
Summary
Confidence
Moderate
Avalanche Summary
No new avalanches in our area but there were three wind slab avalanches just to the north. These were triggered naturally and with ski cuts. They ranged in size from 1 to 2.5.
Although persistent and deep persistent avalanches have been on the decline, it is important to keep it on our radar as incoming snow takes time to settle.
Snowpack Summary
New snow will be falling on a snowpack that within its top 50 cm contains several layers that could pose a threat with this new load.
Faceted snow, surface hoar (3 to 10 mm), and a crust are already buried 10 to 20 cm down. The surface hoar is found in sheltered areas up to 2200 m and the crust is present on steep solar aspects. At high elevations, new snow will be covering up older wind slabs.
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 to 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
Friday Night
Mostly cloudy, 8 to 20 cm accumulation focused mostly in the eastern areas of our region, winds northeast 15 km/h gusting to 50, treeline temperatures falling to -10 C by morning.
Saturday
Increasing sun, trace accumulation ending in the morning, winds northeast 15 km/h gusting to 40, treeline temperatures -15 C.
Sunday
Sunny, no accumulation, winds northeast 25 km/h, treeline temperatures -20 C.
Monday
Sunny, no accumulation, winds southwest 20 km/h, -15 C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Wind slabs may be poorly bonded to the underlying crust.
- Storm slabs in motion may step down to deeply buried weak layers resulting in very large avalanches.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Problems
Wind Slabs
Low density snow that fell Friday evening will be accompanied with moderate to strong winds that will be switching direction from southwest to northeast. New wind slabs will develop on older wind slabs and potentially a crust that was created from warming on Thursday.
Eastern parts of our region may see significant more snow fall than the rest. In these areas and in areas where wind has not affected the snow, expect the storm snow may have present slab properties at all aspects and elevations.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
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
Valid until: Jan 28th, 2023 4:00PM
