LA CROSSE, WI (Ben Caxton) — If radar screens are to be believed the area may be about to be swarmed by the annual fish fly invasion. The National Weather Service in La Crosse reported seeing a hatch on radar Monday evening. It’s not the first. a few smaller hatches were reported to have been seen by forecasters last week. Normally the smelly, slimy bugs appear for a few days just once or twice a year but can hatch multiple times throughout the summer if conditions are just right. Jeff Boyne with the National Weather Service in La Crosse reminds drivers the bugs can be a hazard causing slippery roads and obstructing your windshield, especially when driving near the river or over bridges.