SpaceX will have their first launch from Vandenberg Air Force Base this Sunday, and there’s a reasonable chance you’ll be able to see the contrail. Look to the west and a bit north. The launch is SpaceX’s Falcon 9 rocket (http://www.spacex.com/falcon9).
And, according to Launch Alert (see Home: http://mailman.qth.net/mailman/listinfo/launch-alert), the launch window is currently scheduled for Sunday morning, September 15 during a 09:00-11:00 PDT. However, keep in mind that launch dates and times are always subject to change.