This is the 100mb forecast for 240 hours away, or 10 days out. I encircled the newly-split polar vortex in black (they are now called vortices), and highlighted the factor that is making this happen. There is a strong ridge that will be in place over the Bering Sea (which does not bode well for the East US' winter, but is Cloud 9 for skiers in the West) that will break up the polar vortex. It appears that one piece of this vortex will spin south into Canada and the Northern Plains, and the other piece will slide into Russia and eastern Asia.
The polar vortex coming into your backyard is nothing to mess with. It has the name polar vortex for a reason. When the polar vortex comes around, you best prepare for temperatures colder than you've seen this entire season. This vortex is carrying air gathered from Greenland, Siberia and far northern Canada, which means that the air that comes around will have traits of those regions. In summary, it's cold.
This polar vortex split (and subsequent warming) will lead to the Arctic Oscillation dropping negative, which would bring cold air south into the US. However, that cannot fully happen until that Omega block high pressure system in the Bering Sea gets out of there.