WASHINGTON - As the world warms, the United States will face more severe thunderstorms with deadly lightning, damaging hail and the potential for tornadoes, a trailblazing study by NASA scientists suggests. While other research has warned of broad weather changes on a large scale, like more extreme hurricanes and droughts, the new study predicts even smaller events like thunderstorms will be more dangerous because of global warming. The basic ingredients for whopper U.S. inland storms are likely to be more plentiful in a warmer, moister world, said lead author Tony Del Genio, a NASA research scientist. And when that happens,...