About 1,000 people may die in the United States in the 1980s as a result of tornadoes, the government predicts, but the toll could be lower if people stayed out of cars and took other precautions. Based on experience during the 1970s, when 986 people died, the National Weather Service predicts about 7,000 tornadoes in the '80s, hitting every state in the union. Studies of a massive 1979 twister that killed 44 peopole in Wichita Fall, Tex., concluded that more than 20 were killed because they jumped into their cars and sped away, hoping to outrun the storm, only to be caught in it. The places they left turned out to be safe. Experts give this advice: If you are in a tornado-prone area, plan ahead on what to do if a twister strikes. Even jumping into a bathrub and covering yourself with a mattress may help. Stay away from windows. Basements are good places to go. If you're in a car, don't try to outrun the storm, it probably can keep up at 60 miles an hour. Instead, try to drive off at right angles to it. One nationally known expert suggests wearing football or motorcycle helmets during tornado watches, because brain damage is a major cause of tornado deaths.