April 28th, 2020 – Local Severe Weather Event
new order lyrics Summary: A pseudo-northwest flow event evolved on the afternoon and evening of April 28th producing widespread severe weather across portions of the Middle-Mississippi Valley and Southern Plains. Damaging winds, large hail, and a couple of tornadoes were observed.
Severe thunderstorms were forecast to develop off a lead wave moving through the lower Great Lakes by late afternoon. There was some uncertainty whether or not the wave would feature decaying convection or re-intensify into a robust severe weather threat across northern Illinois. Environmental conditions weren't extremely ripe for severe weather as marginal low-level moisture, filtered sunshine, and less than ideal instability really tempered a more significant severe weather event. Still, however, wind fields were supportive of supercell structures and if ingredients blended just right a low-end tornado threat would develop with any sustained supercell.
The Storm Prediction Center outlined an area most at risk for severe weather during the late afternoon which barely clipped the Chicago metro area. A severe thunderstorm watch (below) was issued shortly after this graphic.
By this time thunderstorms were developing and rapidly strengthening from approximately the Interstate 88 corridor south and west through northern Missouri. Of greatest interest to me was the storm that was moving just north of Interstate 80. It was associated with convection moving out of eastern Iowa and redeveloped on an instability axis that had developed across northwestern Illinois. Due to relatively close proximity to a warm front, this storm exhibited at least some mid-level rotation during its life. There were even a couple of rotating wall cloud reports, but I am not very convinced this storm was ever close to producing a tornado.
The Storm Prediction Center highlighted the storm of interest and noted a marginal severe threat as the storm moved toward the Chicago metro. Quarter sized hail was noted to the west near Newark.
By the time I had reached the storm, it had exhibited some evidence of mid-level rotation. The storm was pulsing up and down over the last hour briefly going severe for hail. The overall environment wasn't the greatest for any strengthening or significant severe weather. I decided to park out ahead of the cell and watch it come in. Of note, some people were commenting on a possible funnel cloud over the Channahon area. This would have been the storm's last attempt to become truly surface-based as scud was ingested into the updraft base. There was no tornado threat evident. I snapped some photos of the storm near Andres and ended up calling it a day and heading home. Photos below.