Avoid avalanche terrain at treeline where triggering the current persistent slab problem is most likely. Remote triggering is possible, always know whats above you.
Wind slabs could be found on north and east aspects in the treeline and above. Strong winds in the alpine mean that wind slab could be found further down slope than expected.
40 to 70 cm of snow sits over a facet-crust weak layer combination that is possible to human trigger. Recent observations demonstrate the potential for this problem to be triggered remotely and release sympathetic avalanches in adjacent terrain. It is most reactive around 1900m.
Friday night: Flurries with winds shifting to moderate from the northwest. Low of -2 at 1400 m.
Saturday: Light flurries in the morning with moderate northwest winds. Freezing level rising to 2000 m.
Sunday: sunny with No new snow expected. Moderate southwest winds and freezing levels rising to 2000 m.
Monday: stormy weather with up to 10 cm of snow and moderate to strong southwest winds. Freezing levels around 1300 m.
Over the past few days several skier triggered avalanches to size 2 have been reported. We believe these avalanches have been failing on the same layer, a layer of facets on a crust from late January. Most avalanche activity on this layer is around 1900m but some have been reported in the alpine as well.
On Tuesday, we received report of a large (size 2.5) human-triggered avalanche near Rainbow Mountain that caught and carried a group of five skiers. The avalanche released on a north aspect at 1900 m. It broke 40 cm deep and ran on the late January facet-crust layer. The avalanche propagated across adjacent roll-over features and triggered a sympathetic slide on a small feature 200 m away.
15 cm of new snow with moderate to strong southwest winds will have formed wind slab on north and east aspects on Friday.
A layer of facets on a crust is now buried down 40 to 70 cm. This layer is widespread between 1800 m and 2000 m, but could be found above and below this elevation band. It has produced several human and remote triggered avalanches in the past few days. In sheltered terrain at treeline surface hoar can also be found on this layer.
Deeper in the snowpack, it is possible to find another crust layer buried down 100-200 cm with facets above it from December. This layer is most prominent between 1700-2100 m and is currently classified as dormant; although large loads such as a cornice failure or avalanches in motion may still be able to trigger avalanches on this layer.
