A huge swarm of mayflies emergence from the Mississippi River near and around La Crosse, Wisconsin on July 20th produced a massive result on radar. It’s not often they swarm in such numbers as to be picked up by radar as rain.
The nuisance bugs cover just about everything once they emerge and nearby residents are warned to cover their mouths and noses.
Mayflies sometimes cause highway accidents. The slippery goo created by millions of mayflies is blamed in a three-car pileup in Hager City, WI yesterday night. A major emergence in 2012 resulted in snow plows being called out to clean up the mess.
The radar detected the flies about 845 pm, emanating from the river (the source) with echo values similar to that of light-moderate rain (35-40 dBZ). With a general south-to-north wind flow above the surface, the mayflies quickly moved north once in the air. As the flies dispersed moving north-northeast, they also gained altitude with some of the echo being detected as far north as Black River Falls and as high as 2500 feet above ground.
via: Wired