Two things going on here:
1) When winds are out of the north, you do have more lake the air can travel over and thus be heated and pick up moisture and lead to LES. So a northerly wind is the best directions for areas from western Marquette County east to areas around Picture Rocks and inland.
2) Radar does not pick up LES very well. Because most of the LES cloud and precip activity happens in the lower levels of the atmosphere and because the earths surface is curved, the radar shoots over the top of the LES clouds. The higher terrain just to the NW of the Marquette radar can also block out some of the signals off to the NW, but it is mostly due to the curve of the earth.
So in a north wind, the western UP is also getting hit with LES, but it is just not showing up on radar. Webcams become your good friend in LES season!
-John