Purcells

Variable new snow amounts mean that new slabs vary in depth and distribution across the Purcells. Transition to a storm slab management strategy as you see new snow depths increase around you.

High -

Saturday night: Mainly cloudy with easing flurries bringing about 2-5 cm of new snow. Strong northwest winds easing to moderate.Sunday: A mix of sun and cloud with isolated flurries and a trace of new snow. Light northwest winds. Alpine high temperatures around -12.Monday: A mix of sun and cloud. Light west winds. Alpine high temperatures around -13.Tuesday: Cloudy with sunny periods. Light southwest winds. Alpine high temperatures around -8 with a mild temperature inversion building toward evening.

Preliminary reports from Saturday in the Golden area describe widespread, small (up to size 1) but touchy storm slabs releasing naturally as well as remotely (from a distance) and with skier traffic in steep alpine terrain. Slab depths were generally from 10-20 cm and increasing over the day.Prior to the storm, avalanche control work on Wednesday and Thursday produced both large and small persistent slab avalanches (size 1 to 2.5) on north facing terrain between 1900 and 2400 m. On Monday and Tuesday control work produced avalanches to size 3 on steep north, northwest and northeast facing features between 1900 and 2700 m. One of the more interesting results was a size 1.5 wind slab that was remote triggered from 200 m away on a north facing slope around 2100 m. On Sunday, a large (size 2.5) persistent slab avalanche was triggered by a snowmobiler in Silent Pass. The avalanche occurred on a wind loaded northwest-facing slope in the alpine. See details in the MIN report.

Saturday's storm brought about 10-20 cm of new snow to the region, burying 5 to 15 cm of older low density snow on the surface. These surface layers sit on a layer of wind-affected snow in the alpine, and in some isolated areas above small surface hoar (feathery crystals).A weak layer that formed during the dry spell in early December is now 80 to 110 cm deep. The layer is composed of facets (sugary snow), surface hoar (feathery crystals), and a sun crust (on south aspects). Another similar weak layer is buried 90 to 150 cm. Finally, the base of the snowpack has weak faceted layers at alpine and treeline elevations. All of these weak layers have been producing large avalanches as recently as December 25th. Human triggering any of these layers is most likely on slopes that didn't previously avalanche and on slopes that have variable snowpack depth (such as rocky alpine features).