When you "analyze" that forecast, it means that it probably WON"T rain!!! Turn it around and it becomes a 70% chance for a dry day.
And as noted, that is the normal forecast. So if it does rain, the forecaster can say "See--we said there was a chance for rain!".
And if it dosen't rain, they say "See-we said there was only a 30% chance for rain!"
The correct forecast no matter what happened!!