Don't let poor visibility or flat light mess with your cornice avoidance when the clouds roll in. Light rain should keep them close to the tipping point and the snowpack close to isothermal.
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.
Cloud cover and light rain may keep (or bring) the snowpack closer to an isothermal state below 2000 m. Other than slushy snow creating difficult travel conditions, it also makes wet loose avalanches possible on steep slopes.
Activity in the region has been on a downward trend, with cornices accounting for most of the interesting recent observations.
A cornice fall above Armchair Glacier was seen 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 with a bit of insulating cloud cover and even rain should work against crust recovery and likely keep the snowpack below 2000 m close to an isothermal state. Rain may fall to around the 2300 m mark, affecting some cornices and up to about 10 cm of windblown old dry snow hiding on north-facing slopes above 2000 m. This snow overlies old wind-affected snow above this elevation and a firm crust below.
Two older crusts exist 1-1.5 m deep at treeline and above. Concern for these layers is limited to high north aspects where large cornice fall may have enough force to trigger a slab, like what was observed on Armchair Glacier on Wednesday. The snowpack below these layers is well settled.
Saturday Night
Coudy with light rain, 4 to 5 mm. 10 km/h north ridgetop wind. Treeline temperature 2 °C. Freezing level 2300 m.
Sunday
Mostly cloudy with scattered showers, 2 to 4 mm. 10 to 15 km/h southwest ridgetop wind, increasing. Treeline high temperature 3 °C. Freezing level to 2300 m.
Monday
Mostly cloudy with scattered showers, less than 1 mm. 30 to 40 km/h southwest ridgetop wind. Treeline high temperature 3 °C. Freezing level to 2000 m.
Tuesday
Cloudy with wet flurries bringing up to about 10 cm of new snow above 1400 m, rain below. 50 to 60 km/h south ridgetop wind. Treeline high temperature -1 °C. Freezing level to 1600 m.
More details can be found in the Mountain Weather Forecast.
