Just a random thought but one thing I've noticed is how much the timing constantly changes between these two systems on the different runs of Euro and especially GFS. For example, hour 138 of 18z GFS had a suppressed southern wave with light snow in NGA. There's essentially nothing on the corresponding hour 132 of the 0z GFS, as the "bulk" of the system seems to have already passed by 18 to 24 hours earlier with a much warmer rain. And there were some runs where the energy from the first wave and second wave seemed to be merged into one system, although that doesn't seem to be the case anymore (the 0z GFS second wave energy seems to just pass way to the south??). So until this gets resolved I would continue to expect potentially significant shifts.