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.
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.
Previous strong wind has created hard, pressed surfaces, wind slab, and scouring in exposed terrain. 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.
Tuesday Night
Partly cloudy. 3 cm of snow. 30 km/h east ridgetop wind. Treeline temperature -4 °C.
Wednesday
Mostly sunny. 3 cm of snow. 30 km/h east ridgetop wind. Treeline temperature -4 °C.
Thursday
Mix of sun and clouds. 20 km/h south ridgetop wind. Treeline temperature -3 °C.
Friday
Mostly cloudy. 10 to 15 cm of snow. 50 km/h south ridgetop wind. Treeline temperature -2 °C.
More details can be found in the Mountain Weather Forecast.
