Northwest Coastal

Human-triggered persistent slab avalanches are still possible in the alpine and treeline where a thick crust does not exist.

Stick to low-angle terrain away from overhead hazard.

Very large persistent slab avalanches continued to be reported around the region through Thursday. Many were reported to have failed on the weak layer from early March, and others failed on the mid-February weak layer. Thursday, multiple size 2 (large) persistent slab avalanches were triggered remotely and by riders, up to 70 cm deep.

Variable wind affect and wind slab covers open terrain at upper elevations. A crust is found up to 1400 m and higher on solar slopes.

Where a thick, supportive surface crust is found, we expect that triggering avalanches on buried weak layers is unlikely.

Three layers of concern currently exist in the upper-mid snowpack. Surface hoar and a crust that formed in mid-March can be found 30 to 70 cm below the snow surface. Below this, another layer of surface hoar that formed in early March can be found at a depth of 60 to 100 cm. Additionally, a layer of facets, surface hoar, and/or a crust from mid-February is buried 120 to 200 cm deep.

The remainder of the snowpack is well consolidated, and there are no current concerns.

Sunday Night

Mostly clear. 15 km/h variable ridgetop wind. Treeline temperature -12 °C.

Monday

Mostly sunny. 10 to 20 km/h northwest ridgetop wind. Treeline temperature -5 °C. Freezing level rises to 1000 m.

Tuesday

Mostly sunny. 20 to 40 km/h north ridgetop wind. Treeline temperature -8 °C.

Wednesday

Sunny. 20 to 40 km/h northwest ridgetop wind. Treeline temperature -4 °C. Freezing level rises to 1200 m.

More details can be found in the Mountain Weather Forecast.

• Be aware of the potential for large, destructive avalanches due to deeply buried weak layers.
• Avoid steep, rocky, and wind-affected areas where triggering slabs is more likely.
• Cornice failures could trigger large and destructive avalanches.