It's spicy out there right now. Between fresh wind slabs and a touchy persistent weak layer, human triggered avalanches are likely. Keep in mind it's not always the first rider who triggers the slab.
Light snowfall and strong winds are building fresh wind slabs in the alpine and open areas at treeline. If triggered, windslabs have the potential to trigger deeper weak layers.
A weak layer of surface hoar sits 40-70 cm deep. Read more about surface hoar on our forecaster blog! Human triggering of this layer is very likely, and has been observed extensively through the region over the last few days even as professionals seek to actively avoid suspect terrain features (eg. convex rolls). Observations are from all aspects and elevations, but especially concentrated on north to east aspects around treeline.
Tuesday night: 5-15 cm new snow. Strong southwest wind. Freezing level dropping to 500 m.
Wednesday: Mostly cloudy with isolated flurries. Moderate northwest wind. Freezing level 500-1000 m.
Thursday: 5-10 cm new snow. Moderate southwest wind, strong at ridgetop. Freezing level 1500 m.
Friday: 10-20 cm new snow. Light southwest wind. Freezing level 1300 m.
Since the weekend, we have seen a surge in persistent slab avalanche activity on the February 22 surface hoar layer. Numerous skier/sled triggered and remote triggered size 1-2.5 were reported by operators across the region even as professionals seek to actively avoid suspect terrain features. In a few instances, slopes were ski cut with no results, only to have the third or fourth skier in the group accidentally trigger the slab. Observations are from all aspects and elevations, but especially concentrated on north to east aspects around treeline.
Natural size 2-4 persistent slabs have also been observed, suspect triggers include sun, wind loading, cornice falls and tree bombs. Explosive control work Sunday and Monday produced results in the 2-2.5 range.
Light snowfall and strong winds are building fresh wind slabs in the alpine and open areas at treeline.
A weak layer of widespread surface hoar sits 40-70 cm deep. It may sit over a crust on solar aspects. The overlying snow has been cohered into slabs by incremental loading through successive storms, wind and mild temperatures. As slab character and depth increase, so do reactivity and size of avalanches failing on the weak layer. Read more about surface hoar on our forecaster blog!
The early February melt-freeze crust down 80-120 cm has not been associated with avalanche activity but is still active in snowpack tests.
