Ascended via east ridge with plans to ski the Box Creek Couloirs. Stayed in hiking boots all the way to summit in the morning, no need for floatation. Snow on the ascent seemed stable, but after traversing over preparing to drop into the couloirs, discovered a 2-4" windslab packed into the couloirs. After evaluating the snow and easily pushing off the stiff top windslab layer, decided it was too dangerous avalanche conditions and retreated climbing back up out of couloirs and descended back down the east route.
Down near treeline, snow went to absolute garbage slush by 1:00pm, collapsing so badly we could not stay afloat on snowboard or skis. Due to delays with backing off the original plan, we were descending later than planned and the postholing was brutal. Saw a group in snowshoes postholing up to their waist, and I was occasionally punching through on my splitboard/skins. Picture is looking down couloir entrance on skier's right.
Photos (click for slideshow):