Strong winds will keep danger elevated at higher elevations. There is still some concern around buried weak layers, and conservative terrain travel will be necessary as we obtain more information.
Up to 60cm of 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 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.
Unstable northwest flow will continue to bring unsettled weather for the next few days. On Friday afternoon, we will start to see the effects of a strong pacific front moving into the northwest ranges.
Wednesday Overnight: A mix up sun and cloud with isolated flurries. 5-10 cm of accumulation overnight. Moderate to strong northwest winds easing slightly and shifting to the west. Freezing levels at valley bottom with alpine temperatures around -15 C.
Thursday: Partially cloudy with flurries, accumulation up to 5cm. Strong westerly winds at ridgetop and alpine temperatures around -15 C.
Friday: Mainly cloudy. Strong westerly ridgetop winds increasing throughout the day and shifting to the southwest. 5-10cm of new snow throughout the day with freezing levels rising to 500m.
Saturday: Overnight, freezing levels reaching 1000-1500m and winds peaking in the early morning strong to extreme form the southwest. 10-15cm of new snow throughout the day, tapering into the afternoon.
Expect natural and rider triggered avalanches to occur as the new snow continues to be redistributed by westerly wind. If you do head out in the backcountry, please share your observations to the Mountain Information Network!
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.
Yesterday's 15-30cm of new snow will bring the week's total to 30-40cm. In sheltered areas, this new snow will remain loose and unconsolidated, but in exposed areas strong westerly winds will 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 will 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.
