Fragile Cornices and Deep Snow on Lincoln Ridge

3 to 4 ft of storm snow existed above the rain crust in the Yuba Pass area. As we toured, hand pits, probing with ski poles, general observations, and formal snowpit data did not reveal signs of slab instability in sheltered areas. We did see settlement cones around some trees indicating consolidation in the new snow. Ski cuts on steep test slopes also caused some small loose dry sluffs.

In more exposed terrain, evidence of wind-loading during the storm included large cornices looming above many wind-loaded slopes as well as wind slabs on wind-loaded slopes. Ski cuts on wind-loaded test slopes did not trigger any shooting cracks or wind slab failures. The cornices above the slopes remained fragile and ski kicks on smaller cornices above test slopes did cause them to fail. When the cornice pieces hit the slopes below they caused some sluffing but did not trigger wind slabs or shooting cracks. Some of the most exposed slopes showed signs of wind-scouring by the NE winds and the rain crust was exposed by wind scouring in a few places along the top of the ridge. The NE winds had calmed down by the afternoon and snow transport was minimal by then.

Photo 1: Cornice drop on a test slope that did not trigger any slab instabilities but did cause a sluff.

Photo 2: Rain crust exposed by scouring on the ridge.

Photo 3: Settlement cone on a tree in below treeline terrain.

Photo 4: Deep crack behind a cornice that has pulled away from the ridge.

Photo 5: ECTN on a sheltered slope. The rain crust/rain layer has started to refreeze but still had some wet snow at the bottom of the layer.