How does doppler radar work?

Radar Update: Snow continues to move further north across the area. We've been receiving several accumulation reports of an inch so far. Expect this area of snow to continue into the afternoon, with areas along the southern edge changing to a rain/snow mix. | US National Weather Service Duluth Minnesota

Radar update! Storms are starting to lose their punch in MN as the sun goes down, but still persisting! NW WI could still see some stronger storms tonight. | US National Weather Service Duluth Minnesota