Roscoe Col Wind Slab Skier Controlled

10-15cm HST offering great powder skiing in less travelled areas. Multiple Sz 1 natural wind slab avalanches observed in Montana bowl from lee/northerly aspects. Skier controlled a P-hard wind slab at Roscoe Col, generated by the moderate S winds gusting to strong. The wind slab avalanche sympathetically triggered another Sz 1.5 slab down to ground. They both slid surprisingly far on a bed of facets. We saw evidence of reverse loading from the past arctic ridge near the Kokanee ridge cat track on southerly aspects. No reactivity from those wind slabs while travelling BTL and at TL. Limited observation in the ALP.