As expected there is a Major "Jet Stream Shift" taking place over the Weekend, and as you will see from the AccuWeather.com Video link, this is already being called a "Giant Dip" in the Jet Stream.
As to why this part of the AccuWeather.com video forecast is not as important as the Eastern States becoming warm it's not clear. The main event come Sunday/Monday is how cold the North Western/Central States will become...more to follow soon.
Note: The "Jet Stream Shift" is a world event not just confined to the USA, look out for other Weather news items in Europe and Asia at the same time.
Click source to see FULL AccuWeather.com Video Link