As ever I find myself agreeing with IO540, maybe it is because he and I seem to do the same kind of intensive flying in GA aircraft.
I did my JAA IR and was taught nothing about weather planning, I did my CPL and was taught nothing about weather planning other than checking the basic met office stuff. The stuff that I had to teach myself afterwards was quite extensive. There are a lot of good resources out there that you discover by trial and error and through people like IO540 that allow you to do more advanced flying. FF if you were taught to subscribe to 3D data and understand skew-T charts as part of your CPL and FI course then you did indeed recieve exceptional training!
I would agree that the average FI is both unable to source that information and would further suggest that they are unable to understand it. Certainly none of them I have spoken to have been able to and in a couple of thousand hours I have met a few!