Stratospheric temperature change is evident in the 240 hour forecast from the ecmwf:
This would favour ridging across greenland, a trough over the bering sea, ridge in western canada and trough over the east.
Remember the fact that modelling is beginning to pick up on this does not necessarily mean that this will occur. It is the observations that i want to look at in order to gain better support for a forecast. Now all of this tropical forcing supports a pattern change to colder weather over central and eastern canada. Now lets see what other indicators we can find too support this. Well we can see the trough recurving east of japan in this time period and AAM beginning to move below normal which supports changes in the pacific, particularly a shift to a -epo and possibly PNA. We need the persistent bering sea ridge to break down in order to bring the cold into the east.