America will become a nation divided with a crippling ice storm gripping the north as ‘blowtorch’ heat roasts the south. A tropical plume surging in from Mexico ahead of the weekend will push temperatures in parts into the mid-70Fs. However, warm moisture hitting cold air from Canada will trigger further storms, experts warn. In the firing line for the highest temperatures, forecast into the New Year, are south-eastern and southwestern states. Jim Dale, US weather correspondent and meteorologist for British Weather Services, said: “Warm air coming up from Mexico will bring a blowtorch blast of…