Local news in Sioux Falls showed traffic at a near standstill on I90 in South Dakota in the Murdo area. There is a 16 mile stretch that drops the interstate to one lane each direction and 65mph speed. Shouldn't be a problem but I guess it does create a bottle neck. One option would be to drop down to hiway 18 and take that into Rapid city. Make sure you fill up at Chamberlain and drop down to 18 west of there, just an option.