6:30 AM Update: New snow and wind may form fresh slabs near ridgetop. Continue to stay aware from overhanging cornices, the most likely trigger for a surprising large avalanche.
20 to 35 cm of snow and southwest winds formed wind slabs on lee aspects at upper elevations a few days ago. Another 15 cm since yesterday may add to these. Slabs may still be reactive on steep slopes immediately below ridgetop.
Cornices have been described as large and overhanging in the Purcells. Cornice failures are dangerous in their own right, but they could also trigger very large and destructive persistent slabs.
Avalanche activity has been tapering in the region and explosives control accounts for most of it. On Thursday, a control route north of the Bugaboos produced three persistent slabs, size 2 to 3.5; the largest propagated widely and ran full path.
A size 2 cornice and size 2 storm slab were among the results, all of which occurred at 2600 m or higher. A few small explosives-triggered and natural wind slab were reported east of Invermere.
If you get out for a look around, post a MIN!
10 to 20 cm of snow over the past day covers a sun crust on solar aspects and otherwise adds to 20 to 35 cm of recent snow, which was redistributed by southwest wind and formed slabs on lee aspects a few days ago. Where sheltered, this snow is settling and bonding well to a thick crust found on all aspects up to at least 2200 m.
Various persistent weak layers may still exist in the top 150 cm of the snowpack and in shallow snowpack areas, depth hoar (large facets) can be found near the bottom of the snowpack. Large triggers, like falling cornices, may be able to trigger these layers at upper elevations where the crust below the recent snow is thin or absent.
Sunday Night
Partly cloudy with scattered flurries bringing up to 5 cm of new snow. 20 to 40 km/h west ridgetop wind, easing. Treeline temperature falling to -10 °C.
Monday
Mainly sunny. 20 km/h west ridgetop wind. Treeline temperature -11 °C.
Tuesday
Mainly sunny. 20 km/h south ridgetop wind. Treeline temperature climbing to -5 °C as freezing level rises to 1500 m.
Wednesday
A mix of sun and cloud with isolated flurries. 20 to 30 km/h southeast ridgetop wind. Treeline temperature -5 °C.
More details can be found in the Mountain Weather Forecast.
