Comment by jachee

Alas, that's just the nature of precipitation maps. When radar is the only true source of what's coming down where, you're a the mercy of the laws of physics, and we don't have a large enough array of stations to give hyperlocal-quality coverage to every locality.

Making it vague-ish was a design choice to help curtail complaints of inaccuracy while still giving near-enough-to-accurate information to be useful generally speaking.