The snowpack is recovering from extreme stress. Very conservative terrain choices are recommended.
Multiple persistent weak layers in the snowpack have been stressed and are primed for human triggering, including remotely from flat terrain.
New snow at higher elevations could form fresh slabs. If triggered, they could step down to deeper weak layers.
A significant avalanche cycle swept through the Columbia Mountains from Monday to Thursday, producing many full-path, size 3 and 4 avalanches. These included persistent slab, storm slab, wet slab, wet loose, and cornice failures.
While natural avalanche activity is expected to decrease on Friday, the snowpack remains unstable and untrustworthy after enduring extreme stress.
Convective flurries may deposit 10 to 20 cm of dry snow at upper elevations, but accumulations will be highly variable. This snow will fall on a wet, rain-soaked upper snowpack. Expect a frozen crust to form across most terrain, except possibly on 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 serious concern for human-triggering and step-down avalanches.
Thursday Night
Partly cloudy with 0 to 4 cm of snow above 1700 m, rain below. 20 km/h south ridgetop wind. Treeline temperature -2 °C. Freezing level 1700 m.
Friday
Cloudy with 5 to 15 cm of snow. 20 km/h southwest ridgetop wind. Treeline temperature -2 °C. Freezing level 1700 m.
Saturday
Mostly cloudy and 5 to 20 cm of snow. 20 km/h west ridgetop wind. Treeline temperature -2 °C. Freezing level 1700 m.
Sunday
Mostly sunny. Calm. Treeline temperature -1 °C. Freezing level 1800 m.
More details can be found in the Mountain Weather Forecast.
