Recent snowfall amounts have been highly variable throughout the region. Any new snow will be especially sensitive to solar triggering when the sun comes out Thursday.
New snow coupled with strong winds are expected to form unstable slabs especially in alpine lees. High snowfall areas including the Howson range and the far north of the region will have a storm slab avalanche problem as well. Fresh storm slab will be especially sensitive to solar triggering when the sun comes out on Thursday.
Recent reports of avalanches on buried surface hoar layers (including this MIN report) suggest that a persistent slab problem has developed. Persistent slabs will become more reactive with the additional load of new snow. While there is uncertainty about the distribution of this problem, sheltered slopes around treeline elevations are most the suspect. Large, deep avalanches have the potential to run below treeline, elevating hazard there.
Wednesday night: Snow with accumulations of 5-10 cm, up to 20 cm in the west of the region, strong wind from the west, alpine temperatures around -12 C, freezing levels drop to valley bottom.
Thursday: Mix of sun and cloud with isolated flurries, moderate wind varying in direction, alpine temperatures dropping to -15 C.
Friday: 10-20 cm of snow concentrated in the south of the region, moderate wind south to southeast, alpine high temperatures around -12 C.
Saturday: Mix of sun and cloud with scattered flurries accumulating 5-10 cm of snow, moderate southwest wind, alpine high temperatures around -8 C.
A large (size 2.5) natural windslab avalanche on a SW aspect at 1700 m was reported from the Howson range on Wednesday.
Reports of persistent slab avalanches associated with buried surface hoar have begun to spring up over the past week. Skier and remote triggered persistent slab avalanches to size 2 were reported on south aspects in the alpine on Tuesday. On Sunday we received reports of recent large natural avalanches in the Telkwa Range (size 2-3), mostly on northeast aspects, many appear to have run on the buried surface hoar layers. A size 1.5 skier-triggered avalanche was reported in the Ashman area on Friday. The avalanche occurred on a convex north-facing slope at treeline and also failed on a surface hoar layer 50 cm below the surface (see full report and photos in this MIN post).
Recent snowfall amounts have varied widely through the region, with only a dusting in the south while northern and parts of the region, as well as along the western border have seen storm totals exceeding 60 cm. Mild temperatures have promoted settlement in the storm snow at lower elevations while wind has loaded lee features in exposed high alpine terrain. Reports suggest there are two layers of surface hoar buried 25-50 cm below the surface. Recent avalanche activity suggest these layers have now become reactive. There is uncertainty about the distribution of this layer, but the sheltered slopes around treeline elevations are the most suspect for having preserved surface hoar.
