Some questions about the Michigan's "Lake Breeze Zone":
* What exactly is it? Does it have to do with an onshore breeze from Lake Michigan?
* How does it work as a boundary?
* How far inland does it extend?
* Does it oscillate back and forth like a dryline?
* Does the east side of Michigan also experience it?
* Is it always a consideration, or is it sometimes stronger, sometimes weaker, and sometimes non-existent?
* Is it seasonal--i.e. nonexistent in winter?
* I've never heard of the Lake Breeze Zone mentioned except in Michigan forecasts. Seems like other Great Lakes states would experience such a phenomenon. Do they?
The Chicago area experiences lake cooling rather frequently in the spring and summer, and maybe our climate can help answer your question.
Note: the lake breeze I'm talking is that generated by the lake itself, not necessarily the effect of synoptic-scale wind patterns blowing lake air around. It generally comes about when surface temperatures over land exceed the lake temperature by about 10 F and surface winds are under about 10 mph. (A converse effect on calm winter days is certainly possible, but I know little about offshore weather during the winter. It may give an extra kick to lake storms along the southern shore of the lake...)
In early spring, the lake breeze is often attended by haze or fog. I've seen clouds of fog blow in off the lake in Chicago and climb over steel facilities in Gary. It's actually quite impressive to watch.
Later in the spring, the lake temperature is rising through the 40s and 50s. In regimes of warm air and light winds, the lake breeze forms in the early afternoon (usually) and can proceed 20-40 miles inland without synoptic support.
Under the lake airmass, I think convection is repressed by two mechanisms. A shallow pool of cool, relatively dry air cuts it off at low levels while, in areas where the lake breeze is divergent like NW Indiana and the south suburbs of Chicago, air sinks and clobbers the convection from above.
At the boundary between lake and Gulf air in Indiana and Illinois, typically winds off the lake run into light yet prevailing west or southwest winds. The air has nowhere to go but up, so convection is favored (but not certain!). Of course, if the lake airmass is marching inland, any convection its inland boundary triggers gets cut off. My guess would be that the boundary between lake and Gulf air in Michigan would not be so sharply drawn on many days as it is on the western shore, if only because winds tend to flow from a westerly direction anyway.
The parts of IL and IN affected by lake breezes vary with the temperature of the lake, the temperature of the surrounding air and near-surface winds generated by synoptic (large scale) systems. That is, the lake breeze travels inland different distances on those days it does develop. And instead of oscillating back and forth, I get the impression that the boundary collapses when temperatures fall at night -- usually inland temperatures fall below the lake temperature every calm night.
Lake Michigan does mess with the weather in fall and winter as well, but usually as part of a larger synoptic situation. Lake effect snows in winter and lake-effect showers in September are the most prominent of such effects, though others have been observed. Occasionally though, mesoscale systems that look like toy hurricanes develop over the lake; they are far weaker than any tropical system.
