North Columbia

Watch for reactive wind slabs at upper elevations that may propagate surprisingly wide on the slick underlying crust.

Treat the danger as CONSIDERABLE if you see more than 15 cm of new snow.

Moderate

• The snowpack structure is well understood.
• We are uncertain about forecast snowfall amounts.

In the past few days, several storm and wind slab avalanches up to size 2.5 have been observed. These avalanches have been triggered naturally, by explosives, and by skiers. Avalanches were predominantly triggered on north and east aspects at treeline and above. The atmospheric river crust has been the failure plane for almost all of them.

Recent strong southwest wind has redistributed snow into deeper deposits on the north and east aspects. Exposed windward features are scoured at treeline and above.

The thick crust that formed as a result of the recent atmospheric river event is found down 40 to 80 cm. This crust extends up to at least 2300 m. Moist snow may be found beneath this crust, particularly at lower elevations.

Weak layers from February can be found down 150 cm and deeper. These layers remain a concern at high elevations where the crust from the atmospheric river might not exist.

Saturday Night

Mostly cloudy. 1 to 10 cm of snow. 30 km/h southwest ridgetop wind. Treeline temperature -5 °C.

Sunday

Mostly cloudy. 1 to 3 cm of snow. 30 km/h southwest ridgetop wind. Treeline temperature -8 °C.

Monday

Mix of sun and clouds. 1 to 4 cm of snow. 20 km/h northwest ridgetop wind. Treeline temperature -10 °C.

Tuesday

Mix of sun and clouds. 1 cm of snow. 20 km/h southwest ridgetop wind. Treeline temperature -10 °C.

More details can be found in the Mountain Weather Forecast.

• Be careful as you transition into wind-affected terrain.
• Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
• Be alert to conditions that change with elevation and sun exposure.