The detour will run from 9 p.m. Friday and 4 a.m. Monday as crews close the toll road between the New Castle and Cranberry interchanges.
That's being done so crews can demolish and replace a bridge in New Sewickley. New construction techniques are being used to replace the bridge quickly.
But the closure also means motorists who try to use that stretch of turnpike will be detoured onto Interstates 376, 80 and 79 to get around it.
Motorists are urged to avoid that stretch of turnpike this weekend, but especially during peak travel hours, because major delays are expected.