Southwest winds became breezy over southeast Wisconsin and Lake Michigan Thursday morning and continued through the afternoon. Wind speeds were generally 15 to 25 mph. The frictional effect of these breezy winds on the surface of Lake Michigan caused the warmer surface water to be carried eastward away from shore. This resulted in upwelling of cooler waters from the shallower near shore areas of the lake, from Sheboygan south to Wind Point.
The below MODIS image from Thursday at 1109 am CDT shows the lake surface temperature had lowered into the upper 50s to lower 60s over portions of the near shore waters, especially east of Sheboygan.
After a full day of those breezy southwest winds, the lake surface temperature had lowered into the middle to upper 50s in the near shore waters from Sheboygan to north of downtown Milwaukee as shown by the below MODIS image from 1016 pm Thursday evening.
The upwelling had little effect on the lake surface temperature in the open waters of Lake Michigan as the lake remains warmer through a deeper layer in this area.
In contrast, here is the image from Monday showing the warmer lake surface temperatures over the near shore waters. The upwelling of the cooler waters lowered the lake surface temperature 10 to 15 degrees.
Surface winds will turn to the northeast today and remain easterly through the weekend. These winds will allow warmer lake surface water to slosh back into the near shore waters of Lake Michigan from Sheboygan to Kenosha.
NWS - Milwaukee/Sullivan