A warm storm approaches from the west bringing new snow, rain, strong wind and rising freezing levels. The storm arrives Mon, and by Tues freezing levels will reach 2500 m. This will cause an avalanche cycle in the region and human triggering will be almost certain in some areas, particularly below treeline and in the Bow Summit area.
A 40–90 cm slab sits atop mid-pack facets and depth hoar at the ground. Many avalanches have failed on both layers with wide propagations (persistent and deep persistent slabs). The potential for remote triggering remains. These problems are slow to heal and will remain with us for some time.
Storm slabs and perhaps even wet slabs below treeline may result from new snow and rain expected on Monday afternoon and Tuesday at all elevations. Be very wary of rain and avoid all avalanche terrain if it rains.
Snow, warmth and rain are coming our way for most of this week. Expect treeline temperatures to reach 2000 m on Monday, 2400 m on Tuesday and even higher on Wednesday. Along with this comes a mix of snow and rain, with some weather models calling for about 10-15 cm of snow overnight into Monday and even rain by Tuesday.
Over the past two weeks, many avalanches up to size 3.5 have occurred, including human-triggered, remote-triggered, and natural slides. These are all on persistent layers often stepping down to the ground. On Saturday, skiers had a near miss with a significant slab near Sunshine Village, and more reports of large avalanches near Observation Subpeak - this area has had very active avalanche activity over the past week.
More new snow and even rain will add an additional load to the snowpack and create new storm slabs for Monday and Tuesday. This sits atop a 40-90 cm dense slab that has settled over a very weak, faceted mid and lower snowpack that fails easily in snowpack tests. This condition is most sensitive in the Bow Summit area. Additionally, slopes below treeline have been unusually reactive and this will continue with the incoming warmth.
