My dog is the same with the ECHO, I'm 100% sure he knows when it's about ten minutes away, and when we are told it's been canclled he doesen't bother going to the door at all.
He also knows when are kitten, his best mate, is outside and barks like mad.... but when it's my other car the one he hates he will sleep by the door as if to say 'Fuck off, nobody can hear you'.
Benni.