snake-
LES can be picked up by radar, but because the clouds and precip from lake effect are quite low in the atmosphere (typically below 10,000 feet) it is not picked up as well as precip that falls from a low pressure system or front.
Thus the further you get away from the radar, the better the chance that the LES clouds and precip is not seen by the radar due to the curvature of the earth. Plus if you have higher elevations in between the radar and the LES clouds/precip, they can block out the signal.
Both cases happen with LES over the western 1/3rd of Lake Superior and from around Baraga west to Ironwood. The radar can be too far away to see the clouds/precip because of the curvature of the earth and there are some higher hills just to the northwest of the radar in Negaunee Township that block out the radars capability of seeing things in the very lowest levels of the atmosphere to it's NW.
It's not because of the higher terrain in the Keweenaw or places around Rockland.
-John