Turbulence is a strange thing, it can be very localised. Before Virgin appeared on the route, we were returning Las Vegas to Gatwick at night, approaching Greenland. From the chat, we knew to expect an 'interesting time' - well the Yanks weren't rabbitting on about the baseball/basketball results, always a good clue! My first officer started plotting the temperature change muttering "We're going to hit it any time now!" BOING - on with the cabin signs, warned the cabin crew - and we sat there waiting for it to start, and hearing all the reports from aircraft being badly bounced around just to the south of us. Nothing. On we cruised, smooth as silk, it turned out to be one of the best Atlantic crossings ever! Weird, eh?
Mind you, Boxing Day 1999, over the Alps. This was the day of The Great Storm in France. The 300mb wind was 300/180 and downwind of Mt.Blanc, descending through the mountain rotor into Turin, that was one of the two occasions in my flying career when I would say I encountered severe turbulence.