Avalanche Forecast
Issued: Jan 20th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Wind Slabs and Deep Persistent Slabs.
wlewis,
Avalanche Canada
Remember the snowpack is weaker than normal, particularly in the Hurley and Birkenhead areas. Safe travel techniques and conservative terrain choices are the best defense.
Avoid areas where the snowpack depth varies rapidly like thin and rocky start zones.
Summary
Confidence
Moderate
Avalanche Summary
No new avalanches have been reported over the last 3 days.
Although not recent, last Saturday's avalanche cycle may be instructive about what's potentially lurking in the snowpack's structure. Hurley was the bulls-eye for avalanche activity on persistent weak layers in the middle and bottom of the snowpack. Surface hoar on the Christmas crust was releasing naturally, intentionally, remotely, and with direct human triggers on gentle slopes near treeline (1800 to 1900 m) with crowns up to 80 cm thick. Some natural avalanches were size 3 to 3.5 and ran full path from the alpine to valley bottom.
Please continue to share any observations or photos on the Mountain Information Network.
Snowpack Summary
The region's generally weak snowpack structure remains.
Up to 10 cm of storm snow is expected to fall over wind affected surfaces at higher elevations, and over a crust at lower elevations.
The late December crust can be found 50-70 cm deep, which is the snowpacks primary weak layer. It is most noteworthy that between 1900 and 1700 m surface hoar can be found above this crust which was reactive last week. This crust varies in thickness with terrain and elevation; in many places it's more of a soft and weak section of the snowpack.
There is a widespread weak layer of facets and depth hoar at the bottom of the snowpack. Snowpack depths around treeline are about 150 cm deep.
Weather Summary
Friday Night
Partly cloudy skies overnight. Freezing levels remain around 500 m. Light to moderate westerly winds. Isolated flurries are possible.
Saturday
Snowfall begins mid morning delivering 5-10 cm over the day favoring the Hurley. Moderate to strong southwest winds. Freezing levels around 500 m. Alpine high temperatures of -3 °C.
Sunday
Clearing skies with light to moderate northwest winds. Freezing levels around 300 m. Alpine high of -5 °C. No snowfall expected.
Monday
Cloudy with isolated flurries. Moderate to strong northwest winds return. Freezing levels around 200 m, alpine high of -6 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Uncertainty is best managed through conservative terrain choices at this time.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Problems
Persistent Slabs
A widespread weakness from late December is found down 50 -70 cm. In some areas preserved surface hoar crystals sit on a crust; in some areas it's just a weak layer in the mid snowpack.
This weak layer has been most reactive in the central and northern parts of the region, particularly around Hurley and Birkenhead .
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Expect fresh wind slabs to build as snow is redistributed by southwest winds. Take care around ridge crests and wind loaded features. Older wind slabs below the fresh snow may still be reactive to human triggers as well.
Be aware that slab avalanches could step down to deeper layers producing larger-than-expected avalanches.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
There are two layers of concern leaving professionals with uncertainty in the region. The first is a crust found down 40 -70 cm that has slowly been improving however in isolated areas weak crystals may surround this layer.
The second is facets and depth hoar in the lower snowpack. These layers are deeper and harder to trigger, but may result in very large avalanches, particularly in warmer temperatures or when load is added. Avoid thick-to-thin areas where triggering deep weak layers is more likely.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Jan 21st, 2023 4:00PM
