Reflectivity is not rain. It is how much energy came back to the radar, which depends on how big and how wet the things in the beam are. Hail throws back a lot. Drizzle throws back almost nothing. That is why a 'light green' return can still soak you and a bright red core can be mostly ice.
The beam climbs as it travels. Sixty miles out, the radar is looking at 6,000 feet, not at your driveway. Everything you see far from the site happened well above your head and may never reach the ground.
Velocity is where the good stuff lives. Red moving away, green moving toward, and a tight red-green couplet means rotation. That couplet is what a warning meteorologist is actually staring at.
Watch the trend, not the frame. One frame is a photograph. Six frames is a forecast.