The NOAA HMS Smoke and Fire Product saw no significant fires today, although the MODIS Aqua satellite image (top left) shows elevated AOD in the Great Lakes. The EPA AIRNow combined AQI loop (top right) depicts moderate to USG AQI in the Great Lakes and Midwest today along with moderate AQIs smattered across the United States. The current high AQI is in Rochester, MN (135) with South Bend, IN being a close second (130).
The OMI NRT tropospheric NO2 column (bottom left) helps explain the raised AQIs in the Great Lakes and upper Midwest, as high levels of NO2 were seen over these regions. Also, going back to the MODIS Aqua image, cloud cover prohibited data over places such as Wisconsin and Minnesota, where some of the highest AQIs have been seen. To the bottom right is a webcam image overlooking St. Paul, MN. From this photo one can see overcast skies, which have persisted throughout the day, and decreased visibility in the area. The main culprit of the AQIs in the area is PM2.5, so it is possible that the low clouds have trapped some of the NO2 concentrations and other aerosols, causing the AQI to increase.