Overcast day with valley fog, some riming. Light wind, no blowing snow observed up to high point at 6,500ft. Traveled on N to NE aspects.
Found buried surface hoar 5-8mm at 1/24 interface (just above crust) on NE at 4000ft. Hand shears revealed this layer easily.
At ~4,200ft an ECT failed upon isolation, on faceted melt forms underneath the crust down 40cm.
Watched a fellow backcountry traveler perform an ECT a few hundred feet above that, with no results on the layer of concern. The crust was down ~60cm here, under thicker snow due to some previous wind drifting.
We observed only very small, underfoot breaking of the crust most of the day, until skiing down a more wind exposed feature. A 20 degree north facing slope at 5,900ft had cross drifted slabs from previous east winds, and each skier noticed large whumphs as they skiied over some of these hidden slabs.