MASON CITY — A slow-moving storm system tracking across Iowa tonight into Friday could bring 1 to 3 inches of rain to North Iowa, raising the risk of flash flooding in Mason City and surrounding communities, according to the National Weather Service office in Des Moines. The National Weather Service issued the outlook at 3:58 a.m. Thursday, warning that heavy rain moving west to east overnight and into Friday morning may overwhelm storm drains and low-lying areas, particularly in cities and towns. North Iowa counties, including Cerro Gordo and Floyd counties, fall within a slight risk zone for excessive rainfall through Friday, meaning scattered flash flooding is possible, according to the National Weather Service. A few stronger storms could bring damaging winds tonight, though the greatest severe weather threat is expected over western Iowa between 8 p.m. and 2 a.m., according to the National Weather Service. Additional thunderstorms are forecast to develop Friday afternoon, with the higher risk for severe weather, including a possible brief tornado, shifting toward southeast Iowa.