18z was the last 'good' operational GFS run and this is why it worked- the NS energy drops in aggressively further west and lifts the southern wave, allowing the developing low to be further nw and gain some latitude as it moves off the coast.
The second image below is the 0z(6z looks essentially the same) and the differences are clear. If you compare the two you can see the differences in the character of the ridge (follow the height lines), which influences the the digging NS vorticity.