New snow and strong southwest winds are forming reactive wind slabs at upper elevations. Caution around leeward terrain features such as ridge crests and roll-overs.
New inputs of snow amid strong southwest winds are forming fresh wind slabs at upper elevations. Watch for freshly wind loaded pockets under ridgecrests and roll-overs.
Monday night: Up to 5 cm new snow, wind increasing to moderate southwest, freezing level 500 m.
Tuesday: 5-10 cm new snow, strong southwest ridgetop wind, alpine high -5 C, freezing level 1000 m.
Wednesday: Trace of snow, light to moderate southwest ridgetop wind, alpine high -4 C, freezing level 1000 m.
Thursday: 5-10 cm new snow overnight, wind easing to light northwest, alpine high -5 C, freezing level 1100 m.
On Sunday a skier controlled size 1 wind slab was reported on a steep, north facing alpine slope in the Duffey area.
On Saturday, small loose wet avalanches were observed on solar aspects at alpine and treeline elevations.
On December 1, a large size 3 natural avalanche was observed on a NE aspect at 2400 m in the Duffy area. It was reported as a cornice failure triggering the slope below and appeared to have slid on the early November crust near the base of the snowpack.
Have you been out and about in the mountains? If so please submit your observations to the Mountain Information Network (MIN). It doesn't have to be technical - photos are especially helpful! Thank you so much for all the great MINs submitted so far!
10-15 cm of new snow (by the end of the day Tuesday) and strong southwest winds are forming fresh wind slabs in the alpine. This new snow falls on soft, dry, possibly faceting snow surfaces in the alpine, a thin melt-freeze crust on solar aspects, and possibly small surface hoar crystals in wind sheltered areas.
The rain crust now sits 30-50 cm deep in the alpine, depth tapering with elevation. In the south of the region, this crust is 10-20 cm thick and supportive. In the north, it exists as a thin zipper crust over 2300 m and may be punchy and unsupportive between 1600 and 2000 m.
In the north of the region, a crust/facet layer sits near the ground. The most recent avalanche activity observed on this layer was on December 1st when a natural cornice fall triggered a size 3. More recent snowpack tests in the Cayoosh zone found this layer down 100+ cm and unreactive. While our uncertainty around the reactivity of this crust is keeping it on the radar going into the active weather pattern over the next week or so, it does not appear to be an active problem at this time.
