A weak layer of surface hoar lucks in the snowpack, problems like this are best managed with conservative terrain choices.
20-40 cm of new storm snow has slowly accumulated over the past few days. Variable wind has formed reactive slabs on multiple aspects, and wind will continue to impact loose snow. Avalanches will be most likely in wind loaded areas and where the snow feels stiff or slabby.
40-65 cm sits above a buried weak layer of surface hoar, facets, and a crust. These slabs have been very reactive to human triggers, showing wide propagations in moderate to low angle terrain, and have been catching people by surprise.
SUNDAY NIGHT - Partly cloudy and isolated flurries / moderate to light northwest wind / alpine low temperature near -24
MONDAY - Cloudy with sunny periods and isolated flurries / light north wind / alpine high temperature near -18
TUESDAY - Sunny / light northwest wind / alpine high temperature near -20
WEDNESDAY - A mix of sun and cloud / light northeast wind / alpine high temperature near -26
As natural avalanche activity tapers, wind slabs and persistent slabs may still be primed for triggering. These may propagate widely and can catch you by surprise even in low angle terrain. Moderate northerly winds are likely building fresh and reactive wind slabs which may be easy to trigger.
On Saturday riders continued to trigger slab avalanches 20-60 cm deep, documented in a handful of MIN reports (Trespass, Mammoth, Spicy, Different Day).
On Friday, there were numerous reports of natural and human triggered persistent slab avalanches up to size 2.5. Some of these were triggered remotely, as outlined in a MIN report that can be viewed here. There were also numerous natural and explosives triggered dry loose, and storm slab avalanches reported up to size 2.
It has been a busy week for avalanche activity, with reports of natural, human, and explosives triggered storm and/or persistent slab avalanches up to size 2 every day for the past week. On Wednesday, persistent slab avalanche activity really picked up and has been a daily occurrence ever since.
Many thanks for all of the great MIN reports over the past week!
20-65 cm of recent snow has formed a reactive slab on top of a persistent weak layer that consists of surface hoar, facets, and a crust that was buried in late January. This sits on top of a plethora of old snow surfaces: hard wind slab, wind-scoured areas, sastrugi, and isolated pockets of soft snow. Below 1800 m a hard melt-freeze crust is underneath the new snow.
A solid mid-pack sits above a deeply buried crust and facet layers near the bottom of the snowpack (150-200 cm deep), which is currently unreactive.
