Radar is an acronym that stands for RAdio Detection And Ranging. A weather radar consists of a parabolic dish (it looks like a satellite dish) encased in a protective dome and mounted on a tower of up to five stories tall. About 150 NEXRAD (NEXt generation of weather RADar) Doppler radars were installed throughout the U.S. in the 1990's. The radar itself does not delineate between rain and snow but AccuWeather's proprietary algorithms do, based on atmospheric conditions. The state-level Snow/Ice/Rain radar images update every 5 minutes on AccuWeather.com Premium, which also gives access to longer loops of radar data. The exclusive AccuWeather.com StormTimer(tm) plots the expected movement of significant storms over the next hour, and also gives access to storm details like hail and rotation. AccuWeather.com RadarPlus offers an interactive weather experience with street-level radar, satellite and lightning data, as well as PredictiveRadar which moves the current radar picture 4 hours into the future.