Increasing wind and snow will build fresh wind slabs throughout the day. Seek out wind sheltered terrain where you can avoid these wind slabs and find great riding.
This week's new snow will continue to be redistributed by strong westerly winds, creating fresh wind slabs in the alpine and treeline. Cold, clear temperatures prior to this storm may have created a weak layer below the new snow, which could increase the likelihood of these avalanches occurring.
An early season crust at the base of the snowpack has shown reactivity in the southeast corner of the forecast region. While this layer likely needs a heavy trigger like a cornice collapse, human triggering may be possible on thin rocky slopes in this part of the region. Be cautious as new snow and wind adds load to the snowpack and tests this deeper layer.
We will start to see the impacts of a strong pacific system over the northwest ranges on Friday afternoon, with the arrival of snow and strong winds. Saturday is looking like a stormy day with a reprieve arriving on Sunday.
Thursday Overnight: Mainly cloudy with isolated flurries, up to 8 cm of accumulation. Moderate to strong westerly winds at ridgetop. Freezing levels at valley bottom, alpine temperatures around - 15 C.
Friday: A cloudy day with increasing wind and snow throughout the day. Strong southwest winds with accompany 5-15 cm of new snow accumulation. Freezing levels at valley bottom wit alpine temperatures around -10C C.
Saturday: Overnight freezing levels rise to around 1000m, up to 15 cm can be expected in the overnight period. A stormy day will follow, 10-20 cm of new snow accumulation. In the afternoon as the system passes, freezing levels drop back to valley bottom, winds ease moderate to strong southwest at ridgetop and snow tapers.
Sunday: A quieter day with a mix of sun and cloud, trace new snow in the morning and freezing levels at valley bottom. Moderate southwest winds at ridgetop.
Large cornices are looming! There have been several natural cornice failures reported in the Bijoux area on Tuesday. This problem will only increase with continued wind transport. Be aware of what is above you, and consider that cornice failures have the potential to trigger deeper layers.
Over the past week, a few large avalanches were observed in the Southeast corner of the region. These avalanches ran on a deep persistent layer, likely one of the crusts from late October or early November.
If you do head out in the backcountry, please share your observations/pictures/conditions to the Mountain Information Network!
This week, the region has seen 30-40cm of new snow. In sheltered areas, this new snow will remain loose and unconsolidated, but in exposed areas strong westerly winds will continue to redistribute this snow into fresh wind slabs in the alpine and treeline.
Prior to this storm, in the south of the region, 5-10mm surface hoar growth has been observed from cold, clear nights on Sunday and Monday. Elsewhere, cold temperatures will have promoted near surface faceting. This has the potential to create a weak layer for new wind slabs to fail on, especially where a crust is present below. As a result, extra caution should be taken as we investigate the bond between these layers.
The lower snowpack consists of a series of early season crusts. Cold temperatures will have promoted faceting around these crusts. Shallow alpine slopes along the eastern side of the Rockies towards Jasper may have weaker, faceted snow near the ground.
Snowpack depths at treeline range from 60cm-200cm, with the shallower value mainly in the eastern side of the range. The alpine snowpack ranges from 150cm-200cm.
