A stretch of northbound Interstate 15 in the northern valley will be shutting down nightly this week, according to the Nevada Department of Transportation. Northbound I-5 will be closed and traffic detoured between 8 p.m. and 6 a.m. from the Lake Mead Boulevard exit to the Cheyenne Avenue exit, said Michelle Booth, a public information officer with the Nevada Department of Transportation. Work will continue Tuesday, Wednesday and Thursday nights, she said.