Avalanche Forecast

Moderate - Forecast snowfall amounts are uncertain

Wednesday night: Flurries bringing 5-10 cm of new snow. Light to moderate south winds.Thursday: Mainly cloudy with continuing scattered flurries bringing approximately 5 cm of new snow. Light southwest winds. Alpine high temperatures around -8.Friday: Mainly cloudy with scattered flurries and 2-4 cm of new snow. Light southwest winds. Alpine high temperatures of -10.Saturday: Mainly cloudy with scattered flurries and 2-4 cm of new snow. Light east winds. Alpine high temperatures of -11.

Reports from Tuesday show a continuation of recent heightened avalanche activity, with numerous storm slab and wind slabs releasing naturally from Size 1.5-2.5 as well as several explosives controlled persistent slabs reaching Size 3.On Monday, many small to large (size 1 to 3) storm slab avalanches were triggered naturally and by explosives at and above treeline on all aspects, 40 to 60 cm deep. Numerous Size 2 to 3.5 persistent slabs were also triggered naturally, by skiers, and explosives at all elevation bands and aspects.These sorts of avalanches have been a consistent trend since last Wednesday, with small to large storm slabs observed at all elevations and large persistent slabs most often observed at treeline and alpine elevation bands. They have been releasing on all three persistent weak layers described in the Snowpack Discussion. Expect to see more avalanches where the weak layers are preserved, such as in sheltered locations in the alpine and treeline elevations and in open cutblocks and gullies below treeline. Triggering such weak layers will likely produce large, destructive avalanches with high consequences.

The current snowpack is complex, with three active weak layers that we are monitoring.60-90 cm of storm snow sits on a layer of crust and/or surface hoar from mid-January. The crust is reportedly widespread, with the possible exception of high elevation north aspects. The mid-January surface hoar is 5 to 20 mm in size and was reported at treeline elevations and possibly higher. 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 80 to 100 cm below the surface. It is composed of surface hoar on sheltered slopes as well as sun crust on steep solar aspects and is found at all elevation bands. Snowpack tests show sudden fracture characters with moderate loads and high propagation potential, and signs of instability such as whumpfs and cracking. Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 100 to 150 cm deep. It is most problematic at and below tree line.A rain crust buried in November is generally 150 to 200 cm deep and is likely dormant for the time being.