Keep an eye on the temperatures. As the snowpack warms persistent weak layers could become more reactive.
Last week 10-25 cm of new snow fell with strong southwest wind creating 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 stepping 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.
A surface hoar layer exists 30 to 40cm above this layer and poses a similar risk
Sunday night: no new snow expected. Low of -5 at 1600m with moderate northwest winds.
Monday: Partially cloudy, light flurries in the morning. Light southwest winds. Freezing level rising to 2000m.
Tuesday: Mainly cloudy with no new snow expected. Moderate to strong northwest winds. Freezing level around 1000m.
Wednesday: sunny with no new snow expected. Freezing level at valley bottom. Light southwest winds.
Several avalanches were reported on Saturday at treeline and above. these avalanches were generally on easterly aspects and ran on either the early January facets or the mid January surface hoar.
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 stepped down to a buried weak layer, we suspect it was the early January facet layer.
Another large natural avalanche was reported 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.
Last week 10-25 cm of new snow was accompanied by strong southwest winds which formed wind slabs in lee areas in the alpine and treeline. 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 center 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.
