Avalanche Forecast
Issued: Feb 3rd, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
swerner,
Avalanche Canada
A persistent weak layer of surface hoar, facets and a crust is buried 30-60 cm down. This avalanche problem is less obvious and harder to predict, so conservative terrain choices are best.
Fresh wind slabs may also be reactive on leeward slopes.
Summary
Confidence
Weather Forecast
Wednesday Night: Snow amounts 5-15 cm. Alpine temperatures near -7 and freezing levels at the valley bottom. Ridgetop wind 30-60 km/hr from West.
Thursday: Mix of sun and cloud. Alpine temperatures near -3 and freezing levels near 1100 m. Ridgetop wind light-moderate from the West.
Friday/ Saturday: Mix of sun and cloud. Alpine temperatures near -12 and freezing levels at the valley bottom. Generally light but gusty winds from the west-northwest.
Avalanche Summary
On Tuesday, reports of a widespread loose dry avalanche cycle occurred in the Babine region. These avalanches were up to size 2 and ran in steep terrain on all aspects and elevations. Wind slabs were also reactive to skier triggers up to size 1 on southwest aspects in the alpine.
With new snow and wind persistent slabs and wind slabs will likely be reactive on Thursday.
Snowpack Summary
Up to 10 cm of new snow fell by Tuesday afternoon bringing 20-40 cm of accumulative low-density storm snow from the past week over a variety of old snow surfaces. These old surfaces include surface hoar in locations sheltered from the wind at all elevations, surface facets, and stiff wind affected snow. On solar aspects, a buried sun crust can be found and a thick crust exists near the surface below 1000 m. Additional snow and wind combined with cohesion may stress these potentially weak interfaces, creating the persistent slab problem.
The lower snowpack has two decomposing crust layers that have been driving a deep persistent slab problem for most of the past month, however, no notables have been reported in the past 2-3 weeks. The upper crust is 70-140 cm deep and continues to show occasional hard sudden results in snow pits. The deeper crust at the bottom of the snowpack is more prevalent in shallow snowpack ranges. These layers seem to be dormant under the current conditions, but shallow rocky slopes should still be carefully assessed and approached with caution.
Terrain and Travel
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Watch your sluff: it may run faster and further than you expect.
Problems
Persistent Slabs
30-60 cm sits above a buried weak interface that consists of surface hoar, facets, and/ or a crust. Forecast snow and strong wind will likely add cohesion and load to these weak layers resulting in a reactive persistent slab problem.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Moderate to strong westerly wind will redistribute the recent snow and form fresh wind slabs in lee terrain in the alpine and at exposed treeline. Wind slabs will particularly be reactive anywhere they overlie surface hoar that was reported to be widespread in many sheltered areas.
Loose-dry avalanches are likely in steep terrain features.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 4th, 2021 4:00PM
