So what is the jet stream? And why is it there? Perhaps your image of the jet stream comes from maps broadcast during the weather portion of your local news. You know the kind: the ones where ...

One knot equals 1.1 mph. The red flags indicate wind direction. For up-to-date maps of the jet stream (and other weather-related maps) visit the FNMOC Web site.

A powerful jet streak could set the stage for the outbreak of severe weather across parts of the U.S. over the weekend.