Slab avalanches are primed for skier and rider triggering. Remote triggering (from afar) is concerning and catching people by surprise. Conservative terrain choices are a great way to handle a persistent slab avalanche problem.
Moderate wind from the west-northwest has redistributed recent storm snow to leeward slopes and terrain features building fresh wind slabs.
Cornices are large and fragile and don't respond well to rapid change- like new load from snow, rapid warming or rapid cooling. They deserve respect and a wide berth from above and below.
A cohesive slab 30-60 cm thick now sits above a buried weak layer of surface hoar, surface facets and crust. These slabs have been very reactive to human triggers showing wide propagations in moderate to low angle terrain. They have been catching people by surprise, so pay attention to signs of instability and stay clear of terrain traps like creeks, cliffs, and depressions below you.
Overnight Thursday: Cloudy with snow 5-10 cm. Ridgetop wind light to moderate from the West. Alpine temperatures near -7 and freezing levels at valley bottom.
Friday: A mix of sun, cloud, and flurries accompanied by a strong West wind. Alpine temperatures near -3 and freezing levels rising to 1000 m.
Saturday: Snow 3-5 cm. Moderate westerly wind. Alpine temperatures low at -20 and a high of -10.
Sunday: Snow 5-10 cm. Ridgetop wind switching to the East and blowing in the light values. Alpine temperatures low of -28 and high of -20.
No new observations by publish time on Thursday.
On Wednesday, numerous natural storm slab avalanches were reported up to size 2, and several more slabs were triggered by explosives up to size 1.5. Loose-dry avalanches were seen up to size 1.
The persistent slab proved to be reactive on Wednesday with skier and rider remote triggers and naturals up to size 2. Check out the awesome MIN posts here: MIN report, MIN report, MIN report. Sending a big shout out of appreciation to everyone posting these MIN's and sharing this pertinent information.
As natural avalanche activity tapers, wind and persistent slabs are still be primed for triggering. These will likely propgate far and can catch you by surprise even in low angle terrain.
Up to 60 cm of recent snow has formed a cohesive and reactive slab that sits above a weak interface of surface hoar and surface facets (weak sugar or feather-like snow crystals) and a crust that was buried late January. This slab of recent snow sits on top of a plethora of old snow surfaces comprising of hard wind slab, scoured areas, sastrugi, and isolated pockets of soft snow. Below 1800 m a hard melt-freeze crust underneath the new snow is found and a surface crust now exists up to 1700 m from the high freezing levels on Tuesday.
A solid mid-pack sits above a deeply buried crust and facet layers near the bottom of the snowpack (150-200 cm deep), which are currently unreactive.
