North Columbia

Very large persistent slab avalanches continue to be reported.

Triggering is most likely on northerly aspects in the alpine.

On Sunday, a naturally triggered size 2.5 persistent slab was reported on a northerly aspect in the alpine.

Numerous skier and cornice fall triggered storm slabs up to size 2 were reported primarily on northerly aspects in the alpine.

Numerous naturally triggered wet loose avalanches up to size 2 were also reported on solar aspects at treeline and above.

10 to 20 cm of snow overlies a wet, rain-soaked upper snowpack. Expect a surface crust to form at night on most terrain, except possibly on high north alpine slopes.

Recent avalanche activity has involved multiple persistent weak layers. The most common failure layer is the early March surface hoar, facet, and crust layer, buried 70 to 150 cm deep.

Many avalanches have also stepped down to deeper weak layers from February and January, buried 150 to 200 cm deep.

These layers are still adjusting to recent stress and remain a concern for human-triggering and step-down avalanches.

Monday Night

Mostly cloudy with flurries, 0 to 20 cm of snow. 10 to 20 km/h west ridgetop wind. Treeline temperature -4 °C. Freezing level 1100 m.

Tuesday

Mostly cloudy with flurries, 0 to 10 cm snow. 10 to 20 km/h west ridgetop wind. Treeline temperature -2 °C. Freezing level 1700 m.

Wednesday

Mostly cloudy with isolated flurries, 0 to 5 cm snow. 10 to 20 km/h west ridgetop wind. Treeline temperature -3 °C. Freezing level 1600 m.

Thursday

Mix of sun and cloud. 10 to 20 km/h north ridgetop wind. Treeline temperature -5 °C. Freezing level 1500 m.

More details can be found in the Mountain Weather Forecast.

• Avoid steep, rocky, and wind-affected areas where triggering slabs is more likely.
• Cornice failures could trigger large and destructive avalanches.
• Triggering deep layers is more likely if the snow surface didn't freeze overnight.
• Use small, low consequence slopes to test the bond of the new snow.