South Columbia

The snowpack is complex and being loaded by new snow with strong winds. Three weak layers are reactive to natural and human triggers at all elevations. The easy solution is to choose simple terrain free of overhead hazard as the snowpack adjusts.

Moderate - Timing, track, or intensity of incoming weather system is uncertain

TUESDAY: Cloudy with light snowfall, accumulation 5-10 cm, moderate to strong southerly winds, alpine temperature near -9 C, freezing level near 500 m.WEDNESDAY: Cloudy with light snowfall, accumulation 15-25 cm, light to moderate southerly winds, alpine temperature -6 C, freezing level near 1000 m.THURSDAY: Mostly cloudy with light snowfall, accumulation 5-10 cm, moderate southerly winds, alpine temperature near -10 C, freezing level near 700 m.

On Sunday, numerous storm slabs and wind slabs were triggered naturally, by skiers, and by explosives. The avalanches were small to large (1 to 2), at all elevation bands, and generally 20 to 60 cm deep, often failing on the mid-January weak layer. Similar avalanches within the recent snow have been observed daily since last Wednesday.Persistent slab avalanches were triggered naturally and by skiers on Saturday, generally at treeline and alpine elevation bands. Most of these avalanches have been releasing on the early-January weak layer, but a few avalanches also occurred on the mid-December weak layer. Although we are seeing general decreasing activity on these layers, expect to see avalanches where the weak layers are preserved.

The current snowpack is complex, we have three active weak layers that we are monitoring.50 to 80 cm of storm snow sits on a crust and/or surface hoar layer (mid-January). The crust is widespread, except possibly at high elevations on north aspects. The mid-January surface hoar is 5 to 20 mm in size and is likely present at all elevation bands. The recent storm snow fell with strong south winds, producing wind slabs in lee features at treeline and alpine elevations and in open areas below treeline.Deeper in the snowpack, a persistent weak layer known as the early-January layer is buried 70 to 100 cm. It is composed of surface hoar on sheltered slopes and a sun crust on steep solar aspects and is present at all elevation bands. Recent snowpack tests have shown sudden fracture characters with moderate loads and high propagation potential, as well as other signs of instability such as whumpfs and cracking. Yet another persistent weak layer buried mid-December is 100 to 150 cm deep and consists of a facet/surface hoar/crust combination. It is most problematic at and below tree line.A rain crust buried in November is 150 to 200 cm deep and is likely dormant for the time being.