Large skier-triggered avalanches occurred this past weekend!
A buried weak layer and developing wind slab will make backcountry travel challenging. Watch out for signs of instability such as whumpfs and shooting cracks and terrain features such as convex rolls and cross-loaded features. Check out our latest blog for how to manage this problem.
Watch out for signs of instability such as whumpfs and shooting cracks and terrain features such as convex rolls and cross-loaded features.
The new snow that has accumulated since Thursday night has begun to be redistributed this snow with winds from the west-northwest amping up.
As this slab builds it will create more load on the weak layer further down. Loading will increase reactivity and heighten the potential for a smaller avalanche to "step down" and create deeper avalanches that connect large swaths of terrain.
Buried layers of surface hoar and facets have been reactive to human triggers in recent days. Reactivity has been observed in sheltered areas at treeline, where the surface hoar may be preserved, and in wind-loaded areas at upper elevations, where a cohesive slab has been formed above.
The connectivity of avalanches through the terrain should be seen as high at the moment.
Avalanche activity has ramped up in the last few days. The most notable report came from a group of skiers who were involved in an avalanche in the Lizard Range. One person was buried but their companions were able to dig them out safely. This avalanche occurred on the mid-November weak layer.
The MIN has similar reports of this layer being triggered and creating large avalanches such as this one from Hosmer. Buried weak layers are difficult to predict and make travel through avalanche terrain a challenge. It seems that we have reached a tipping point and avalanche activity on this layer can be expected to continue.
A huge thank you to those who have supported the community and reported in the MIN.
Since Thursday night up to 30 cm of snow has fallen. This is expected to be redistributed by west-northwest winds that have picked up since Sunday night. New wind slabs are expected to form on a variety of surfaces. In the alpine and at treeline on the northeast aspects, it sits mostly on older wind slabs. In more sheltered areas the newer lighter snow sits on about 20 to 30 cm of more consolidated snow. Just below this is where our mid-November weak layer, consisting of facets and surface hoar. A widespread rain crust remains near the ground, at the treeline, and below the treeline.
At treeline, snowpack depths vary from 120 to 200 cm.
Monday Night
Clear with cloudy periods, no accumulation, winds north 8 km/h, temperature -13 C at 1500 m.
Tuesday
Sunny with cloudy periods, trace accumulation, winds northwest 10 km/h, temperature -9 C at 1500 m.
Wednesday
Cloudy with possible sunny periods, up to 3 cm accumulation, winds west 10 km/h, temperature -12 C at 1500 m.
Thursday
Cloudy with sunny periods, 2 cm accumulation, winds northeast 10 gusting to 25 km/h, temperature -12 C at 1500 m.
More details can be found in the Mountain Weather Forecast.
