Strong winds have created stiff wind slabs in the alpine and treeline.
These wind slabs may be fairly stubborn to human triggering but have the potential to step down to deeper weak layers, resulting in large destructive avalanches.
Earlier in the week, 10-25 cm of new snow fell with strong southwest wind created hard wind slabs in lee terrain features. These slabs may be stubborn to human triggering but have the potential to step down to deeper buried weak layers creating large avalanches.
A weak layer of facets (sugary crystals) formed from prolonged cold temperatures in late December has shown recent reactivity as increased load has combined with warm temperatures. A noticeable trend is that these large, destructive avalanches are occurring in wind-loaded areas, with failures initiating as a wind slab and steeping down to this deeper layer. Extra caution should be taken whenever the snowpack is being tested with increased load, warm temperatures, or strong solar radiation.
Saturday Overnight: Cloud cover increasing, light snow in the early morning. Moderate to strong westerly winds. Freezing level dropping to 500m.
Sunday: Mainly cloudy, light snowfall. Light to moderate northwest winds. Freezing level rising to 1000m.
Monday: Partially cloudy, trace precipitation. Light to moderate northwest winds. Freezing level rising to 2000m.
Tuesday: Mainly cloudy, light snowfall. Moderate to strong northwest winds. Freezing level around 500m.
On Friday, a large natural avalanche was reported near Smithers on Hudson Bay Mountain, the details can be viewed in this MIN report. The avalanche appears to have initiated as wind slab and stepping down to a buried weak layer, we suspect it was the early January facet layer.
Operators reported another large natural avalanche on Friday afternoon in the Telkwa Range, north of Starr Basin, which also appeared to have run on the early January facet drought layer. These avalanches are an indication that the recent storm and warming temperatures have put enough load on the upper snowpack to 'wake up' this previously dormant layer.
Earlier in the week, 10-25 cm of new snow was accompanied by strong southwest winds formed wind slabs in lee areas in the alpine and treeline. Westerly winds will continue to redistribute available snow into fresh wind slabs. Below 1200m, this new snow landed on a melt-freeze crust.
Two weak layers may exist in the upper snowpack. First is a layer of surface hoar that may be found around 30 cm deep. To date, this layer has produced avalanches in the centre and north of the region and not the south, though it has been found in the south. Next, a widespread layer of faceted grains is found around 30 to 60 cm deep, which formed during the cold spell in late December and early January. The recent storm has shown the potential for wind slabs to step down to this early January layer.
In thin snowpack areas, the base of the snowpack is composed of weak faceted grains around various melt-freeze crusts, which are considered dormant at this time.
