Avalanche Forecast

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

TUESDAY: Mostly cloudy with intermittent snowfall, accumulation 1-3 cm, moderate to strong southerly winds, alpine temperature near -10 C, freezing level near 500 m.WEDNESDAY: Mostly cloudy with intermittent snowfall, accumulation 1-3 cm, moderate southerly winds, alpine temperature -7 C, freezing level near 600 m.THURSDAY: Mostly cloudy with light snowfall, accumulation 5-10 cm, moderate to strong southerly winds, alpine temperature near -10 C, freezing level below valley bottom.

On Sunday, a large (size 2) storm slab was remotely triggered by a skier on a southeast aspect, 50 cm deep, at treeline.  Other avalanches likely released, but there were limited observations in the region because of the stormy conditions.Many avalanches were reported on Saturday (with conditions indicated as Spicy).  Small to large (size 1 to 3) storm slabs and wind slabs were observed, being triggered naturally, by skiers, snowmobiles, and explosives.  The avalanches generally released on lee slopes (northerly to easterly) at all elevation bands, ranging from 30 to 90 cm deep.  Many of the avalanches released on the persistent weak layers described in the Snowpack Summary.  Similar avalanches were observed on Thursday and Friday.

The current snowpack is complex, with three active weak layers that we are monitoring. 30-60 cm of storm snow sits on a crust and/or surface hoar layer (mid-January). The crust was reportedly widespread; high elevation north is likely one of the few crust-free zones. The mid-January surface hoar is up to 10 mm and reported 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, the early-January persistent weak layer is 30 to 70 cm below the surface. It is composed of surface hoar on sheltered slopes and sun crust on steep solar aspects and found at all elevation bands. Snowpack tests show sudden fracture characters with easy to moderate loads and high propagation potential, as well as whumpfs and cracking. Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 40 to 100 cm deep. It is most problematic at and below tree line.A rain crust buried in November is 100 to 150 cm deep and is likely dormant for the time being.