Avalanche hazard exists where the wind has loaded cornices and drifted recent snow into wind slabs. Give cornices a wide berth and assess for wind slab conditions before committing to terrain.
Winds have drifted the recent storm snow into slabs in leeward terrain that may be possible to human trigger. Winds have shifted from extreme out of the southwest to moderate out of the northwest, creating a tricky loading pattern in the alpine and potentially bringing cornices to their breaking point.
Sunday night: Cloudy, isolated flurries with 2-5 cm of snow, light southwest winds, alpine temperature -15 C.
Monday: Mostly clear, light northwest winds, alpine high temperature -10 C.
Tuesday: Increasing cloud, isolated flurries with trace accumulations, light southwest winds, alpine high temperature -11 C.
Wednesday: Cloudy, 10-20 cm of snow, light to moderate southwest winds, alpine high temperature -8 C.
During the storm, numerous large (size 2-3) avalanches released naturally in the storm snow. These avalanches primarily occurred on leeward aspects and mainly at treeline and alpine elevations. A very large cornice fall was reported Sunday on a north aspect at 2400 m, and it stepped down to a large slab avalanche. Below tree line, large wet loose avalanches were releasing naturally on Friday and into Saturday.
There have been three notable natural avalanches reported over the past three days in the north of the region. These were very large (size 3-4) persistent slab avalanches breaking 100-250 cm deep on southeast, east, and northwest slopes above 2000 m. These avalanches add to the previous two observations of very large persistent slab avalanches over the past week. Although the likelihood is decreasing in the aftermath of the storm, easier-to-trigger wind slab avalanches or large cornice fall may have the potential to step-down to this layer in isolated areas.
There have been substantial changes to the snowpack over the past few days. 40-80 cm of snow fell during the weekend storm above 1900 m. Higher snow totals fell in the northeastern parts of the region. Extreme winds originating from the southwest and shifting to the northwest have created a tricky loading pattern in the alpine and have elevated concern for cornice triggers. These winds drifted the snow into deeper, stiffer slabs on leeward terrain features that may be possible to human trigger. During a warming event Saturday night, rain saturated snow surfaces up to around 1900 m that have since refrozen with cooling temperatures.
The mid and lower snowpack is generally well settled and strong. In the north of the region, a weak layer of surface hoar buried 90 to 170 cm deep may persist in isolated areas.
