I'd expect to see it at around 15-20 miles under good conditions. The closer you are to the radar head, the more chance you have of being seen. I don't know the geography around N Yorks but ATC radars are basically "line of sight", although other factors come into the equation - for example the location of buildings adjacent to the radar head in the direction of the target and, in basic terms, whether the radar in question is tuned for low cover.