I tried to attach hours 54-102 of the 6z GFS plot I posted above, but it exceeds the amount of MBs allowed. But if you go to TT and GIF between those hours, you can really see the dynamics occurring. The wave breaking around 60W is the initial confluence. It slightly relaxes as the STJ storm is moving along the GOM, which gives it a chance to gain latitude, but then the northern stream energy comes flying in to finish the job. You were correct in asking about the high pressure because it is "blocking" the storm, but the mechanism keeping the high so stoutly in place are the items I mentioned.
IMO, to get this storm to shift north, the vort energy diving into Quebec will have to come in delayed or further north. For that to happen, the tropospheric wave break will need to be less intense.
Also, there has been discussion about better ridging out west(Boise ID rule) that could help. In theory that is true, however, the retrograding wave break will to be the driver once the storm reaches the east coast.
I hope you get to use your snow blower!