Heading up to Tri Chutes we assessed stability at ~9800 ft (W-NW aspect), ~10500 ft (SW aspect), and ~10600 ft (N aspect) with a set of ECTs. We found that the new snow and layer beneath was not propagating all the way across the column and would only do so with lots of force (forgot the exact failure), breaking on an ice layer interbedded with graupel. Seeing that Tri Chutes was wind blown and rocky up top we chose to ski the main and skier's left chutes of Birthday Chutes. The first skier hooked right into the main and skied the middle of the chute without any signs of instability. The second and third skier/splitboarder took the left chute. I went last and entered into the main chute where the first skier entered but decided to stay higher on the sub-ridge. After a few turns I rolled over a wind lip (trending N) and immediately took a ski cut which slowly released a slide under my skis and I began to see rapid propagation ~100 feet below me. The slide began at my skis, barely NE, but did not carry me. Furthermore, the loose storm slab broke at the ice layer. (Notice first skier's turns trending more NW compared to the NE slope I triggered) After the slide I chose to stick to the trees between chutes, but dealt with some loose-dry.