On May 20th, I decided to chase along a cold front that was entering northwest Illinois during the afternoon and evening. I targeted Dubuque, IA along the U.S. 20 corridor seeing the potential for some supercells to initiate along a cold front. By midday, I was already traveling north to get in the vicinity of my target and to re-evaluate. The area I was targeting featured 2,000J/kg of CAPE, 0-6km shear at 40kts, and a moistening boundary-layer with dew points rising to near 65°F. Supercells initiated by early evening along the U.S. 20 corridor in northeast Iowa and northwest IL. They would quickly explode into severe thunderstorms with copious amounts of hail. I sat for a good hour or so watching and photographing a supercell near Galena, IL. These supercells struggled to get organized in terms of low level organization and rotation. They actually looked high-based visually. That doesn't mean they were anything to sneeze at though as these storms dropped some big hailstones that I stayed away from near Dubuque, IA and Galena, IL. The first supercell I could tell was high-based and just a hail producer so I waited for another supercell near Dubuque, IA to head southeast and cross the Mississippi River giving me options to chase it. I ended up heading south on IL Rt. 84 just north of Hanover, IL hoping to get a good visual in a difficult area of terrain. I grabbed a few photos of a rotating mesocyclone. It was in the process of dissipating unfortunately. After seeing too many storm mergers convectively overturning the target area I decided to head back home on IL. Rt. 78. by late evening. I added a few photos form the chase day in northern Illinois below:
That catches you up on this particular chase day. I would chase the next day as well on May 21st in east-central Illinois. I'll update with that post at a later date.
