Avalanche Forecast
Issued: Jan 19th, 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.
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Avalanche Canada
Ride like it's the Rockies! Hurley and Birkenhead are the bulls-eye for a poor snowpack structure. Despite the MODERATE rating, manage your risk through conservative terrain choices, implementing safe travel techniques in your group and adopting a defensive mindset.
Summary
Confidence
Avalanche Summary
No new avalanche reports Tuesday or Wednesday.
On Monday cornice chunks released slabby pockets in cliffy terrain below.
Although not recent, last Saturday's avalanche cycle may be instructive about what's portentially 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.
Thanks for the observations and please continue to post your reports and photos to the Mountain Information Network. It is really helpful for forecasters!
Snowpack Summary
The region's generally weak snowpack structure remains.
Surface: At high elevations there may be some lingering wind slabs. At lower elevations last week's rain or wet snow has frozen into a crust.
Mid-pack: 50 to 70 cm below the surface is the late December weakness -- this appears to be the snowpack's primary critical layer. In some areas it's a crust and it's 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-weak-rotting section of the snowpack.
Lower-pack: 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
Thursday Night: Cloudy with clear periods and isolated flurries. Precipitation: Trace. Alpine temperature: Low -10 °C. Light southwest wind. Freezing level at valley bottom.
Friday: Sunny with cloudy periods. Precipitation: Nil. Alpine temperature: High -4 °C. Light west wind. Freezing level at valley bottom.
SaturdayFlurries. Accumulation: 5 to 10 cm. Alpine temperature: Low -9 °C, High -3 °C. Moderate southwest wind occasionally gusting to strong. Freezing level at valley bottom.
SundaySunny. Precipitation: Nil. Alpine temperature: Low -10 °C, High -7 °C. Mostly light northwest wind occasionally gusting to 35 km/h. Freezing level at valley bottom.
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.
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 soft, weak, rotting layer in the mid-pack. 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
Watch for wind-affected areas where pockets of wind slab may linger.
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 healing however in isolated areas weak crystals may surround this layer.
Secondly, the lower snowpack is made up of facets and depth hoar. The new load and prolonged warm temperatures may trigger deep layers resulting in very large avalanches.
Give the snowpack a few days to settle with the new load before discounting deep persistent weak layers. Avoid thick-to-thin areas where triggering deep weak layers is more likely.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Jan 20th, 2023 4:00PM
