Avalanche Forecast
Issued: Mar 6th, 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.
astclair,
Avalanche Canada
Recent snow and wind have formed reactive wind slabs at upper elevations that remain possible to human trigger. A buried weak layer warrants a conservative mindset and terrain use strategy, particularly in the south of the region.
Summary
Confidence
Weather Forecast
Friday night: Mostly clear, light variable winds, alpine temperature -12 C.
Saturday: Partly cloudy, isolated flurries with trace accumulations, light variable winds, alpine high temperature -7 C, freezing level at valley bottom.
Sunday: Mostly clear, light southwest winds, alpine high temperature -7 C, freezing level at valley bottom.
Monday: Mostly clear, light southwest winds, alpine high temperature -5 C, freezing level 1000 m.
Avalanche Summary
On Wednesday and Thursday, a natural cycle of large to very large (size 2-3) avalanches released in the recent storm snow, primarily on wind-loaded aspects (northeast, east, and southeast) above 1800 m. Several were triggered by large cornices failures.
Over the past week, there have been many reports of persistent slab avalanches releasing on the Feb 22 surface hoar. These avalanches primarily occurred on north, northeast, and east aspects between 1400-2100 m. Check out this MIN for a helpful illustration of where you might expect to find this problem.
Snowpack Summary
Incremental snowfall and strong winds continue to build wind slabs in the alpine and open areas at treeline. A few sun crusts exist on solar aspects in the upper snowpack. Convective snowfall in the wake of the storm may obscure the evidence of these wind slabs.
A weak layer of surface hoar may be found 60-100 cm deep. There is uncertainty about the distribution and reactivity of this layer, especially in the north of the region. Sheltered slopes near treeline are most suspect. Read more about surface hoar on our forecaster blog!
Below a melt-freeze crust down 80-120 cm from early February, the snowpack is well settled and strong.
Terrain and Travel
- Stay off recently wind loaded slopes until they have had a chance to stabilize.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Use conservative route selection and resist venturing out into complex terrain.
- Even brief periods of direct sun could produce natural avalanches.
Problems
Wind Slabs
Incremental snowfall and strong winds have formed large, reactive wind slabs in the alpine and open areas at treeline. If triggered, wind slabs have the potential to trigger deeper weak layers. This problem also overlaps with where cornices may be reaching their breaking point.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar may be found 60-100 cm deep, and human-triggering remains possible. Over the past several days, large (size 2-3) natural and human-triggered avalanches have released on this layer. Observations are concentrated to north, northeast, and east aspects near treeline. This problem has been observed in all but the northern tip of the region, where there is uncertainty around the distribution of this layer.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 7th, 2020 4:00PM
