Yes, the GEM evolution is interesting, particularly when you compare it and the UKMO one with GFS.
GEM develops a LP system in the upper mid-west and deepens it rapidly as it hits the ocean off the eastern seaboard - but then the energy hits the block and most of it is forced north with just a tiny part spinning south under the block.
The UKMO evolution is harder to read because of the 24 hour steps but attempts something not too dissimilar.
GFS, in marked contrast, doesn't generate any WAA from the LP exiting the eastern seaboard and thereafter there is nothing to stop the jetstream coming east.
So, as early as Day 5 to Day 6 there are significant differences in the handling of the block and the next bout of energy coming out of the US. Until the modelling of that is tied down the subsequent evolution is up in the air.
ECM will be interesting..... again......
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E