missle launch california

There’s fairly a buzz in the blogosphere about this video shot by a KCBS News helicopter. Explanations range from “Moonbeam Gov. Jerry Brown is head home to visit relatives” to “missile launch reserved secret by the Pentagon”.
What it is, I’ve seen not anything like it. The speed doesn’t match a missile, but the route and cloud pattern surely seems to. . One alert reader “slp” posted in comments a link to a likely Occams Razor style explanation.