Bad weather contributes to major accident on Interstate 40 in OklahomaA major winter storm brought a rare white Christmas to the southern US plains, contributing to a 21-vehicle accident that shut down Interstate 40 in Oklahoma.The storm system surging east from Kansas and the Texas Panhandle brings the threat of tornados and severe thunderstorms along its southern fringe, from south-east Texas to Alabama, said the National Weather Service.The storm is expected to bring blizzard conditions and 6-8 inches (15-20cm) of snow as it strengthens and moves north-east into the upper Ohio River valley through southern Missouri and Illinois.Freezing drizzle overnight led to 10 separate collisions on Interstate 40 at Oklahoma City just before 3am, said the Oklahoma highway patrol.The 21-vehicle crash forced the closure of the westbound lanes for about five hours.