Snowing hard off and on, mixed graupel. The old wet snow surface went from soft, spongy, and partly supportable to hard, slick, and fully supportable in an hour or 2. The new snow piled up 3-4 in deep and every slope over about 30 deg or maybe a little less that we crossed slid at our feet. Sluffs were traveling fast and far and entraining a lot of snow. Fun and amusing until one caught my feet, very nearly carried me over a steep rollover, and ran fast for several hundred vertical feet past me. Partnership management became an issue because getting hit from above was a real threat. The bed surface was hard, shiny ice and sliding for life was a secondary threat. Riding conditions were actually fast and fun on slopes less than about 10 deg in steepness but everything else was hard and slick but at least smooth. I'd call the danger considerable and very unlike anything we normally see. High likelihood (virtual certainty) with low consequences that could quickly get out of hand on a long open steep slope with terrain hazards. Snowing hard when we left.