This animated JET STREAM FORECAST shows how the northern and southern streams are to combine or "phase" to generate the vertical motions in the atmosphere which will drop Central U.S. barometric pressures precipitously---generating wind and significant precip in the process. The color scheme highlight wind velocities. Note how a powerful phased "wind max" develops aloft over the Central U.S. in this animated forecast. It's that wind max that is to drive rapid intensification of the winter storm

The jet stream, a fast moving ribbon of air, has a significant influence on our weather. The position of the jet stream this week will drive a move away from low pressure to bring high once again over the UK. This will in turn bring more settled weather for most of us. Here are the details… | Met Office