BD, the Nav Can displayes allow for an overlay to be added to the screen which is a blue colour (as I mentioned, 2 intensities). It doesn't obscure the radar at all, and given the lag time, you eventually do see wx in a position aircraft were diving around 15 mins ago. I think it could be a great idea, if it were current information.
How does a controller 'know' if the weather displayed by radar is bad enough such that a plane could not fly through it?
If it's Air Canada, you'll know
