Excellent post.
One thing I'm watching for wrt end of Jan into Feb is how the Alaska ridge evolves or trends. The GFS ensembles want to retrograde it SW to the Aleutians, causing the crazy warm SE ridge look. But the Euro ensembles have it split down the middle, 50% retrogrades it NW and makes a poleward ridging connection, keeping the cold across the CONUS. The other half is split between the GFS look and a compromise between the two (which is still "just cold enough" for us). The run-to-run trends are favorable so far, though. Definitely gonna keep an eye on this because it could open up more opportunities for a SECS/MECS in February.