RMR Slackcountry; Montana Bowl; Rosco's

Sz 1.5. North Aspect. 2170m. Triggered from ridge top while assessing wind effect on the slope. Fracture pulled back onto ridge top, pulling me into the feature a few metres. Bed surface was very hard to edge on hence the sliding into the slope. Avalanche was 30m wide x 100m long, with a 20-40cm crown. Interface was 2mm facets and 5mm surface hoar on top of 3cm temp crust. Slab was 20cm of 4F over 10-20cm of F snow.