Drive along an English road and you will soon see a sign giving you “Advanced Warning” of forthcoming roadworks. We do lots of roadworks and advanced warning is always given.
I try not to be a pedant but I smile. When you give warning in advance that something is going to happen, you give an Advance Warning not an Advanced one.
Part of the explanation of the error lies in sound similarity: say “advance warning” quickly and it sounds more or less the same as “advanced warning”. But this coincidence does not explain why the makers of road signs have picked “Advanced” rather than the grammatically correct “Advance” for their signs. Since the sounds are more or less the same, why pick the wrong one when it comes to spelling?
I think there must be a chain of association to other uses of “Advanced”. For example, in England, school students take exams called “Ordinary Levels” when they are about 16 and more difficult – more advanced – exams when they are 18. The latter exams are called “Advanced Levels”. These are not Levels in advance of something, but Levels which are more advanced than something else, namely Ordinary Levels.
By analogy, an Advanced Warning would be a warning more advanced than some other kind of warning – for example, an Advance Warning. That is not the kind of warning road sign makers are giving you. But they have very often seen the words "Advanced Level" in print - they are a regular newspaper topic and, in addition, sign makers' children may well bring home bits of paper about Advanced Level courses. The sign makers then just go with the flow of words they have read in quite other contexts.
I suspect that in time, “advanced warning” will take over from the grammatically correct “advance warning”, just as we now refute things when in fact we reject them and you just have to live with it.
Here, for example, is the 11th March 2014 front page of the Financial Times – normally pedantic about English grammar:
“…the wealthy would find ways around the proposed tax grab, especially now they have had so much advanced warning …”
I suppose that is one of the problems when you are of advanced years – you see these things coming in advance.