We have some uncertainty in the likelihood and distribution of persistent slabs. In times of uncertainty, conservative terrain choices are the best defense.
Wind slabs may be triggerable on a variety of aspects at upper elevations.
Wind slabs may step down to deeper layers, resulting in larger avalanches.
Persistent weak layers of crust/facets or surface hoar are buried in the upper 250 cm of the snowpack. Distribution seems spotty and signs of instability may not be evident. The best defence is choosing smaller, low-consequence terrain.
On Tuesday, a couple of natural wind slabs, size 2-2.5 were observed on east aspects in the alpine.
Several recent natural cornice falls have been large enough that even without triggering a slab they were size 2.5 or greater.
A handful of very large persistent slab avalanches have been reported throughout the region in recent days. Some are suspected to have run on the mid-March layer, and others even deeper. Most of these avalanches were triggered by cornices.
5-10 cm of new snow sits over firm, wind-affected surfaces. A sun crust could be on or near the surface. Cornices are large and overhanging.
A layer of facets and/or surface hoar from earlier in March can be found 50 to 100 cm deep.
Several older persistent weak layers are buried up to 250 cm deep. While triggering these layers is trending toward unlikely, they present a low-probability, high-consequence problem.
Wednesday Night
Mostly clear skies. 10 km/h southeast ridgetop wind. Treeline temperature -3 °C.
Thursday
Mostly sunny. 20 km/h southwest ridgetop wind. Treeline temperature -4 °C.
Friday
Mostly cloudy. 5 to 10 cm of snow. 50 km/h south ridgetop wind. Treeline temperature -3 °C.
Saturday
Mostly cloudy. 2 to 5 cm of snow. 30 km/h southwest ridgetop wind. Treeline temperature -3 °C.
More details can be found in the Mountain Weather Forecast.
