Severe weather sweeps U.S. with hail, tornadoes threatening multiple states

Twice in as many days, the American sky reminded its inhabitants of nature's indifference to human routine. A hail-driven assault on Minnesota's Twin Cities Friday night was not an ending but a beginning — the same restless atmospheric system turning southward by Saturday, where conditions were ripening for tornadoes across a broad stretch of the South. In the space between a weather alert and a warning siren lies the oldest human calculation: how much time do we have, and what must we do with it.