SIOUX FALLS, S.D. — Strong storms are moving into the Midwest, dumping heavy snow in South Dakota, spawning a tornado in Nebraska and threatening dangerous thunderstorms from Oklahoma to Wisconsin.

A foot of snow had fallen by this morning in western South Dakota’s Black Hills thanks to a storm slowly moving in from Colorado and Wyoming.

National Weather Service meteorologist John Chamberlain said the fall storm is one of the most intense to hit the area in a long time.

No travel is being advised along some western South Dakota roads, and some schools canceled classes. As much as 30 inches of snow could fall in the area.

Large hail and powerful winds are forecast to hit northwest Oklahoma later today, while storms were forecast from there into Wisconsin into Saturday.