Keep an eye on those cornices! One more sunny day of exploring before the clouds roll in. Bring sharp tools for the crust and start and finish early to avoid getting caught in isothermal snow.
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.
Slushy, isothermal snow conditions often emerge on sun-facing slopes during the heat of the day. Plan your route with this in mind to avoid getting surprised by difficult travel and rising wet loose avalanche danger.
Activity in the region has been on a steady downward trend.
A cornice fall above Armchair Glacier was reported Wednesday, suspected to have failed 12 - 24 hours earlier. It triggered a slab on the slope below, likely on one of the persistent layers mentioned in our snowpack summary. Collectively, it amounted to size 3.
Explosives control in the Duffey on Monday produced small wet loose avalanches and a few slabs to size 1.5. One failed on the 30 - 40 cm-deep late-March crust.
Spring-like melt-freeze cycles now characterize a daily evolution of surface conditions on all but north-facing slopes above 2000 m, where about 10 cm of dry snow may still be found. It 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 mid and lower snowpack are otherwise well settled.
Thursday Night
Clear skies. 10 to 20 km/h southwest ridgetop wind, increasing. Treeline temperature 3 °C. Freezing level 2500 m.
Friday
Sunny. 20 km/h southwest ridgetop wind. Treeline high temperature 4 °C. Freezing level 2600 m.
Saturday
Mainly cloudy with scattered showers, 1 to 3 mm. 5 to 10 km/h southwest ridgetop wind, easing. Treeline high temperature 3 °C. Freezing level 2500 m.
Sunday
Mostly cloudy with light rain, 2 to 4 mm, and a possible trace of new snow in the alpine. 10 km/h east ridgetop wind. Treeline high temperature 4 °C. Freezing level 2400 m.
More details can be found in the Mountain Weather Forecast.
