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

10-day jet stream forecast video showing the atmospheric river hitting the west coast next weekend into early next week, before lifting to the north. | Magaliaweather.com