This is the main action for the winter.
I did Greenland yesterday, but now I noticed that Alaska is just as active. The physics at work here, is density flow. That is, the air mass over the Arctic is much denser than the surrounding air, due to intense cold.
This dense air acts as a headpond for a leaky dam. If a spill starts, it etches its way into forming a channel of cold. That can be persistent for the winter. Looking at the historical records for the Little Ice Age, it wasn't super-cold every winter. To me, that meant that the spillways keep changing. There are 4 zones, with a low elevations where the spills can take place.
Siberia, Alaska, Canada, and Greenland. Last winter, it was Siberia, and that spill flooded California. This summer, it has been Canada all the way. Now, we have Alaska and Greenland.
I had assumed that Canada would have priority over Alaska, since it has been going all summer, but it is a close contest. So, we watch and wait.
ps. This is the Wheel of Cold, where it stops, nobody knows.