Weird wind

Bumped into some weird wind slab at the end of our first pitch in the RMR backcountry. We’d seen evidence of wind slab walking out towards Montana trees that had been ski cut by patrol. We didn’t hear any whumpfing etc while skinning. Skied the first pitch after south bowl with a mix of catchy wind skin and some softer powder. I skied the pitch and went to stop towards the old cat road and set off this small pocket. It was supported from underneath by the cat road so it didn’t move anywhere but the slab was 15 -20cm thick on the old wind affected surface from Jan 14th ( I may have this date wrong). It propagated across approx 25m. We walked up the road and dropped into the trees further south , the snow in the trees was soft and did not have the same wind affect but snow was still slightly funky from the cold.