Several changes aloft when taking a look at things...
-Lead wave on Mon/Tue is a bit further south, and ends up tracking further south overall.
-PV in Canada is much further south, which helps shunt the overrunning potential south.
-Main trough in the West is much more stung out/elongated and it slower, thus you end up with a much slower ejecting main storm system. Also ends up further SE than the GFS has it, do to a lot of what is mentioned in other points.