Use caution on and below ridge crests where cornices are present.
Large cornices still loom over many ridgelines and they won't hang on forever. Be aware of overhead hazards and stay back from cornices on ridges.
This region is the most likely in the Southwest for a cornice fall to trigger a surprise slab.
As freezing levels come down wet loose avalanches will become unlikely. It may still be possible to trigger this problem on steep slopes where surface snow remains moist or isothermal.
A few small wet loose avalanches were reported on Saturday.
A cornice fall above Armchair Glacier was seen on Wednesday, suspected to have failed 12 - 24 hours earlier. It triggered a slab on the slope below (adding up to size 3), likely on one of the persistent layers mentioned in our snowpack summary. A second size 2 cornice fall on a NE aspect at about 2500 m was observed by another group in the Duffey corridor.
Sustained high freezing levels, combined with cloud cover and periods of rain, are limiting crust recovery and will likely keep the snowpack below 1800 m weak and near isothermal. As freezing levels drop, a surface crust is expected to form at higher elevations.
Two older crust layers exist 100 to 150 cm deep at treeline and above. These layers are not a widespread concern, but on high north aspects, large cornice falls may have enough force to trigger a slab, similar to the recent event on Armchair Glacier. The snowpack below these layers remains well settled.
Sunday Night
Mostly cloudy. 1 mm of precipitation as snow or rain at treeline. 20 km/h west ridgetop wind. Treeline temperature 0 °C. Freezing level 2100 m.
Monday
Mostly cloudy. 40 km/h southwest ridgetop wind. Treeline temperature -1 °C. Freezing level 1800 m.
Tuesday
Mostly cloudy. 1 to 10 cm of snow. 50 km/h southwest ridgetop wind. Treeline temperature -4 °C. Freezing level 1500 m.
Wednesday
Mix of sun and clouds. 3 to 5 cm of snow. 30 km/h west ridgetop wind. Treeline temperature -8 °C.
More details can be found in the Mountain Weather Forecast.
