Avalanche Forecast
Issued: Mar 3rd, 2020 5:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
Wind slabs have been reactive lately and will continue to build with light overnight snowfall and strong winds. Fresh snow will be especially sensitive if the sun comes out Wednesday.
Summary
Confidence
Moderate - Uncertainty is due to extremely variable snowpack conditions reported through the region.
Weather Forecast
Tuesday night: 5-10 cm new snow. Strong west wind. Freezing level dropping to valley bottom.
Wednesday: Mix of sun and cloud with isolated flurries. Moderate northwest wind. Freezing level valley bottom.
Thursday: 5-10 cm new snow. Strong southwest wind. Freezing level 1500 m.
Friday: 10-20 cm new snow. Light southwest wind. Freezing level 1000 m.
Avalanche Summary
On Monday and Tuesday several large natural wind slabs size 2-3 were observed on northeast to southeast aspects in the alpine. Some were triggered by cornices failures.Â
Over the last few days, persistent slab avalanches were reported, running on the surface hoar layer. Skier triggered size 1-2 on north to east aspects in the alpine, and natural size 2-3 in steep alpine terrain with a few size 2 observed below treeline. Natural wind and storm slabs size 1.5-3 were observed on north to east aspects in the alpine on Sunday.
Snowpack Summary
Incremental snowfall and strong winds continue to build deep pockets of fresh wind slab in the alpine and open areas at treeline.
A weak layer of widespread surface hoar sits 60-90 cm deep. There is uncertainty about the distribution and reactivity of this layer especially in the north of the region. Read more about surface hoar on our forecaster blog!Â
The early February melt-freeze crust down 80-120 cm has not been associated with avalanche activity but still gives results in snowpack tests.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- 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 buried surface hoar.
- Brief periods of sun could quickly initiate natural avalanche activity.
Problems
Wind Slabs
Light snowfall and strong winds are building fresh wind slabs in the alpine and open areas at treeline. If triggered, windslabs have the potential to trigger deeper weak layers.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar sits 60-80 cm deep. The overlying snow has been cohered into slabs by incremental loading through successive storms, wind at upper elevations and mild temperatures at lower elevations. As slab character increases, so do reactivity and size of avalanches failing on the weak layer (surface hoar). Read more about surface hoar on our forecaster blog!
Skier triggering of these persistent slabs is likely, and has be observed over the last few days even as professionals seek to actively avoid suspect terrain features (eg. convex rolls). Observations are concentrated on north to east aspects around treeline.
This problem has been observed mostly in the south of the region. There is uncertainty around the distribution of the surface hoar problem in the north.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 4th, 2020 5:00PM
