DES MOINES, Iowa (AP) — Heavy snow has blanketed much of northern Iowa, snarling traffic and closing schools and services, as a late winter storm moves through the region. Online reports issued by the Iowa Department of Transportation show snow and ice covering roads in north-central Iowa and partially covering roads for much of the rest of the northern half of the state. The National Weather Service has issued a winter storm warning for three dozen counties in Iowa’s northern half and a winter weather advisory for several more counties in the region. The weather service expects some areas to see up to 8 inches of snow by Monday afternoon.