A ‘multi-day severe weather event’ threatens large parts of the US with heavy rain and hail, tornadoes, and powerful supercell thunderstorms. As California battles the worst snowstorm for a year, volatile weather driven by vast temperature differences across America is about to hit eastern states. Heavy rain will bring a risk of flooding through the coming days before wind and hailstorms hit ahead of the weekend. Low pressure sweeping eastwards on a strong jet stream will bring ‘multiple rounds of storms’, experts warn. This could include supercell thunderstorms–strong storms with a tornado-li…