Bell's Couloir size one slab triggered

Size one slab triggered by skier on the way up bell's couloir below the middle cliffband on NNE aspect, failed on skiers foot, no one caught Slab thickness ~ 20cm, 20m wide, air temp: -4°C, slope in the shade no solar aspect, debris went down to the fan Lots of dry loose off the big cliff on the lookers right of the couloir due to rising solar impact throught the sunny morning, maybe small cornice failure