Its certainly legal to fly through the AIRMET. These are advisories covering large areas. But it behooves you to determine that your flight plan wont enter known or forecast light or moderate icing conditions as prohibited in 91.527. Here goes. Theres a stationary front just west of the route, bringing in cloud layers and scattered showers. Freezing levels will hit between 7000 and 12,000 feet. So, at 8000 feet, you do risk picking up ice. One lone pilot report from a single-engine turbine over Iowa shows negative ice in climb from 3000 to the tops at 11,000. This isnt all that useful since youre flying lower and slower, but you are willing to climb as high as 12,000 feet to be on top. Your Plan B, while not at all mission-friendly, is to turn back to warmer air and land in Iowa, or even return to Bowling Green if thats best.