Weak layers in the upper snowpack are primed for human-triggered slab avalanches. Evaluate snow and terrain carefully and remember; conservative terrain choices are your best defense.
Recent snow and wind have formed wind slabs in leeward terrain features at upper elevations. They may be especially reactive where they sit over a slippery crust or surface hoar.
A widespread weak layer of surface hoar/crust/facets is buried around 30 to 40 cm deep. There have been several cases of skiers being surprised by it recently. Most were on north to west aspects near treeline.
Each day over the past week, several persistent slab avalanches are reported across the region. They are:
Natural and human-triggered, some remotely from large distances away.
Average size 1 but up to size 2.
On north to west aspects, mostly around treeline.
Failing on the late-January layer described in the snowpack summary.
15 cm of new snow settles over a complex upper snowpack.
A widespread breakable crust sits beneath the new snow, on all but the highest north aspects. At mid elevations, it may be topped with surface hoar crystals, making for a weak bond.
Another widespread weak layer is buried 30 to 40 cm deep. It formed in late January and consists of surface hoar on a melt-freeze crust, with a thick layer of facets below. Check out the snowpack test results on this layer in this MIN from Friday.
These layers are expected to become increasingly problematic as they get buried deeper.
The mid and lower snowpack remain well settled, with no significant concerns at this time.
Sunday Night
Mostly clear skies. 10 km/h west ridgetop wind. Treeline temperature -5 °C. Freezing level 1000 m.
Monday
Mostly cloudy. 1 to 4 cm of snow. 20 km/h west ridgetop wind. Treeline temperature -7 °C. Freezing level 1500 m.
Tuesday
Mostly cloudy. 1 to 2 cm of snow. 20 km/h southwest ridgetop wind. Treeline temperature -7 °C. Freezing level 1300 m.
Wednesday
Mostly sunny. 20 km/h northwest ridgetop wind. Treeline temperature -7 °C. Freezing level 1300 m.
More details can be found in the Mountain Weather Forecast.
