Using radar data, a forecaster can determine the nature of any existing weather systems and follow their movement and evolution. This is a valuable tool for making short term weather predictions.
This QuickTime movie (964k) shows severe thunderstorms moving across Illinois. By analyzing radar loops such as this, forecasters can determine the intensity and movement of thunderstorms, helping them to issue advanced warnings and advisories to cities which lie in the paths of the storms.
This QuickTime movie (803k) shows a large area of heavy rain developing around St. Louis. After seeing this area develop on radar, meteorologists issued flood watches for Missouri and southern Illinois.