Seiche
Short period fluctuations occur in amounts varying from a few inches to several feet and for periods varying from a few minutes to a day, depending on the locality where they occur. These changes, and by oscillations called seiches, which may be caused by one or both of the other two. Sustained winds drive forward a greater volume of surface water than can be carried off by the subsurface return currents, thus raising the water level on the lee shore and lowering it on the windward shore. This effect is more pronounced in bays and at the extremities of the lakes, where the impelled water is concentrated in a small space by converging shores, especially if coupled with a gradually sloping inshore bottom which even further reduces the flow of the lower return currents. Closely spaced high and low barometric pressure centers moving across a lake cause a temporary tilting of the water surface. The amount of this tilting is dependent of the pressure gradient and the speed of the moving centers. Seiche (pronounced saych) is an oscillation that occurs when winds and/or barometric pressure differences causing a fluctuation have diminished. The lake surface is in a tilted condition, and a surge of water takes place from the high area to the low. An imbalance in the opposite direction occurs and causes a return surge. This effect continues, with each successive surge diminished by friction until the seiching action cease.
To make a long story short (I know, I know), a long duration or strong west wind piles the water up along the Michigan shoreline. When the wind stops quickly, the water come back. Warnings are issued.