Very large natural persistent slab avalanches continue to be reported on deeply buried weak layers.
Strong solar radiation and warm temperatures increase the likelihood of triggering.
Very large natural persistent slab avalanches continue to be reported on deeply buried weak layers. Strong solar radiation and warm temperatures increase the likelihood of triggering.
Triggering slabs will be most likely on wind affected slopes at upper elevations.
Expect strong solar radiation to trigger small wet loose avalanches.
Keep in mind that small avalanches in motion may step-down to deeper weak layers.
On Friday, several naturally triggered size 3 persistent slab avalanches were reported on northerly aspects at treeline and above, near Trout Lake.
A significant avalanche cycle swept through the Columbia Mountains from Monday to Thursday, producing many full-path, size 3 and 4 avalanches. These were primarily persistent slabs that were triggered by rapidly rising temperatures, snow/rain, cornice falls, and smaller storm slabs in motion.
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.
Saturday Night
Clear skies. 5 to 10 km/h east ridgetop wind. Treeline temperature -5 °C. Freezing level valley bottom.
Sunday
Sunny. 10 to 20 km/h east ridgetop wind. Treeline temperature 1 °C. Freezing level 2100 m.
Monday
Mostly cloudy. 10 to 20 km/h southeast ridgetop wind. Treeline temperature -2 °C. Freezing level 1800 m.
Tuesday
Mostly cloudy with flurries, 5 to 10 cm snow. 10 to 20 km/h west ridgetop wind. Treeline temperature -1 °C. Freezing level 1900 m.
More details can be found in the Mountain Weather Forecast.
