The northern stream piece to this puzzle is just now coming on shore along the northern Canadian Pac coast and southern Alaskan coast. The last of the "big" changes would occur by roughly 6z tomorrow as the last of that onshore data gets ingested. Honestly, it is pretty amazing it didn't move much today. I suspect it is pretty well sampled now, but that might be part of the reason the 18z GEFS ticked south. My guess is this trends a hair south for about 12-24 more hours and then begins to lift back north. Been going on all winter w/ storms. The real interesting thing right now as deterministic runs increase snow totals....are ensembles now playing catchup? The 18z GEFS is starting to reflect deterministic totals.