Avalanche Forecast

Moderate -

Wednesday night: Flurries bringing approximately 5 cm of new snow. Light to moderate south winds.Thursday: Mainly cloudy with continuing isolated flurries and a trace of new snow. Moderate to strong south winds. Alpine high temperatures around -8.Friday: Cloudy with isolated flurries and a trace of new snow. Light south winds. Alpine high temperatures of -10.Saturday: Cloudy with isolated flurries and a trace of new snow. Light variable winds. Alpine high temperatures of -12.

No new avalanches were reported in the region on Tuesday. Activity in the adjacent North Columbias included 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, there was evidence of a widespread natural storm slab cycle with very large avalanches being released (up to size 3.5). This occurred on all aspects, at all elevations, with depths of 40 to 100 cm, and generally occurring on the mid-January weak layer but sometimes on the mid-December layer. Also, a large (size 2.5) persistent slab avalanche was triggered by a skier at treeline, which stepped down to the mid-December weak layer. The slab was 65 cm deep and slid on a 30 to 35 degree north-facing slope.These types of avalanches are a continuing trend, showing that our snowpack is capable of producing very large, destructive avalanches even in relatively shallow terrain. Expect similar avalanches to release at all elevation bands where these buried weak layers are preserved.

The current snowpack is complex, with three active weak layers that we are monitoring. 30-70 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 surface hoar is up to 10 mm is size and has been 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 found 40 to 90 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 with skier traffic. 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.