Blocking has failed to develop once again, leading to warm anomalies across most of the U.S. overall. There are some signals indicating we could see a prolonged turnaround in temperatures towards the second half of the month, but it looks like the warmth will control the pattern overall through January. Arctic air could start to intrude into western Canada around mid-January, and that would make it much easier to bring negative anomalies into the central and eastern U.S. IF we can get some blocking in the Atlantic.
The start of January will be cold in the East as an Arctic air mass moves through, but this should be transient in nature as the PNA ridge spikes in the western U.S. before fading into a -PNA regime. Aboves return by the end of week one and holds through at least week two. It’s going to be a tough balance between the aboves and belows in the central U.S. if the colder air can start to intrude into the U.S. from western Canada.
Here’s a look at the previous January forecast for comparison: