although 18z nam looks pretty similar on the surface as 12z, there were subtle enough differences, (trend?) on the 500h map that if it were to continue would probably lead to a flatter solution similar to the euro. Less phasing of the northern stream and a broader trough.
frustrating I can't post maps/images
for us central ohioans.... subtle = HUGE In the end it's going to be those tiny nuances in the northern and southern stream and the development of the trough that could sink this 20 miles one way or another.