Seems to happen to me at least once each summer, completely socked in with fog.
Skied to the summit as part of the Moat Lake circuit. Would not recommend ski descent from Frink and down around Castlecrags-hard to find the route and have to cross a bad avalanche slope to get out. We had very stable conditions, but the route is not too nice in that direction in winter.
As part of the high circle tour taking in Castlecrag, Frink and across to the NE ridge of Albert Edward. A long (13.5h) solo day car to car covering ~35km and ~1,100m of elevation gain. Cloudy at times but otherwise perfect, cool weather. Saw only one other party all day whilst descending AE.