As a cold front passed through the area on the afternoon and evening of 5/11/2012, a few interesting features showed up on the NWS Marquette radar. The image below is the radar reflectivity at 7:00pm EDT. First, the cold front is depicted by the darker blue, wavy line passing through western and northern Marquette county. Normally, fronts will have a much more linear appearance. However, the lack of friction over Lake Superior and the assistance from cooler air over the lake allowed the front to progress quicker. The result was the front actually passing through the city of Marquette earlier than in Negaunee. The same thing happened earlier in the day across the Keweenaw Peninsula, where Houghton showed a frontal passage much earlier than Twin Lakes even though both should have experience the frontal passage at the same time if it were truly a line.
Another interesting feature is the faint, darker blue line in eastern Marquette county. This is the boundary between the cooler air from Lake Michigan and the warmer air originating over land. Persistent south winds during the day allowed temperatures to stay cooler across eastern Upper Michigan.
When these two features met across central Marquette county, a few showers resulted between Marquette and Gwinn.
Because these boundaries are fairly shallow features, they are only detected close to the radar.