A surprisingly strong surface low-pressure system is expected to move through the Northern Plains and south-central Canada in the middle of the week, creating what the National Weather Service identifies as a considerable severe weather threat for nine northern states in the US. The Storm Prediction Center has indicated that Wednesday will be the most perilous day, with the possibility of large tornadoes, winds reaching 80mph, and flash flooding from the Dakotas to the Upper Midwest and Great Lakes. A cold front will draw Gulf moisture upward, creating conditions that meteorologists caution could lead to an unprecedented outbreak in a typically calm early June.
