Heavy snowfall in the Upper Midwest
1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) include an overlay of GLM Flash Extent Density — and showed the distinct circulation of a middle-tropospheric closed low (400 hPa analysis) as it moved northeastward across Illinois and Indiana into southern Lower Michigan on 25 March 2023. Isolated clusters of brief lightning activity were seen across the region, but there were no reports of thundersnow. A number of locations in Iowa, Illinois and Wisconsin received heavy snowfall, with several new daily records being set.The corresponding 1-minue GOES-16 “Clean” Infrared Window (10.3 µm) images below helped to highlight areas of mesoscale banding where precipitation rates were enhanced (some sites reported snowfall rates of 1 to 2 inches per hour).
Later in the day, as clouds cleared along the back edge of the storm system, much of the southwest-to-northeast swath of fresh snow cover was revealed in GOES-16 Day Snow-Fog RGB images (darker shades of red) and Day Cloud Phase Distinction RGB images (brighter shades of green).Microwave estimates of snowfall rate (SFR) are available at this website, and imagery during the day on the 25th are shown below. The heavy band of snow is apparent early in the morning of 25 March; by afternoon, it has shifted eastward to hug the Lake Michigan shoreline in Wisconsin.