Avalanche Forecast
Issued: Mar 6th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Cornices and Persistent Slabs.
ldreier,
Avalanche Canada
Strong to extreme northwest wind will continue to form wind slabs and grow cornices. Buried weak layers are at prime depth for human triggering and were reactive to skier traffic in the last few days.
Summary
Confidence
Weather Forecast
Sunday night: Cloudy, up to 5 cm snow, extreme northwest wind, alpine low -4 °C, freezing level dropping to 600 m.
Monday: Mainly cloudy with sunny periods, up to 2 cm snow, moderate northwest wind, alpine high -5 °C, freezing level at 1000 m.
Tuesday: Sunny, moderate to strong northeast wind, alpine high -10 °C, freezing level at 500 m.
Wednesday: Mix of sun and cloud, moderate to strong northeast wind, alpine high -8 °C, freezing level at 300 m.
Avalanche Summary
There have been a few, skier triggered slab avalanches to size 2 on the two buried persistent weak layers described in the Snowpack Summary in the last few days.
A skier triggered a large (size 2) avalanche on a north aspect in the alpine on Saturday. The avalanche released on a crust and was about 70 cm deep.
On Friday, a natural large slab avalanche was observed on a northeast aspect that likely released on the buried surface hoar layer. Skiers triggered small (size 1) avalanches on a northeast aspect on the same layer. A natural cornice fall triggered a wind slab on the slope below and resulted in a size 2 avalanche.
A professional operation reported a slab avalanche being triggered by a wet loose avalanche from above on Thursday. And skiers triggered a size 1.5 slab avalanche from a distance away. It likely released on the buried surface hoar layer.
Snowpack Summary
There's a lot going on in the upper snowpack. Careful assessment is recommended.
There is a crust on the surface at lower elevations and on solar aspects at treeline.
Feathery, weak surface hoar crystals buried around February 26th are found down 25-50 cm, most prominently at treeline elevations. This layer has been reactive to skier traffic in the last few days.
A thick crust buried in mid-February is now found down 60-100 cm. Skiers triggered avalanches on this layer in the last few days.
The lower snowpack is effectively bridged by the layers above, and we do not expect avalanches to be triggered in the lower snowpack at this time.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid travelling on slopes below cornices.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Be aware of the potential for large avalanches due to the presence of a buried crust.
Problems
Wind Slabs
Strong to extreme northwest wind will continue to form fresh wind slabs where loose snow is available for transport. Wind slabs might develop farther down slope than expected due to the strength of the wind.
Triggered wind slabs might step down to deeper buried weak layers and result in larger avalanches.
Aspects: North East, East, South East, South, South West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Cornices
Extreme northwest wind will grow cornices even larger. Avoid slopes with cornice hazard above. Keep in mind that firm cornices can pull back into flat terrain at ridgetop if they fail.
Aspects: North, North East, East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Persistent Slabs
A layer with weak, feathery surface hoar crystals is buried 30-50 cm deep at sheltered treeline features and in the lower alpine.
A thick crust is buried 60-100 cm deep. Avalanches on this layer will likely reach large sizes.
A few, skier triggered avalanches and isolated natural activity up to size 2 were reported on both layers in the last few days.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 7th, 2022 4:00PM
