A weather system already punishing the Midwestern United States with the coldest temperatures of the winter was forecast to spin to the south and west on Wednesday, prompting ice storm warnings and likely hazardous travel conditions. The cell of arctic high pressure sitting over Canada that has driven temperatures some 20 or 30 degrees below normal in the U.S. Midwest and northern Plains will bring even rougher weather as it moves into central and southern states, the National Weather Service said. “We have very cold air across Canada that will continue to funnel down into the central portion of the United States for the next several days,” said meteorologist Lara Pagano of the weather service. “This is actually going to be a prolonged period of well below normal temperatures.” Wind chill advisories have already been issued for northern U.S. states, including Montana and North Dakota. As temperatures drop further south …