MIDWEST — A confirmed tornado outbreak took place in southern Illinois on Sunday, which included a Particularly Dangerous Situation (PDS) tornado confirmed in Gibson County, Indiana. This severe weather event contributed to Illinois reaching 173 tornado reports, exceeding its previous yearly record of 126 set last year.

Storms developed along a front extending from the mid-Mississippi Valley to the central High Plains, bringing the possibility of large hail, damaging winds, and tornadoes. Approximately 1.5 million people were under a Tornado Watch, and severe storms had the potential to produce EF-2 or stronger tornadoes with wind gusts exceeding 70 mph.

A Flood Watch was issued across the region through Sunday night, with an increased Level 3 out of 4 flash flood threat in place. Multiple rounds of thunderstorms were expected to drop 1 to 3 inches of rain, with localized totals potentially reaching 5 to 8 inches in areas where storms repeatedly tracked over the same locations.

An expansive storm system moved eastward across Missouri and Illinois on Sunday morning, leaving behind a residual outflow boundary. A mesoscale convective vortex (MCV), defined as a robust area of low pressure with its own warm and cold fronts, remained after these morning storms. New storms developed into mini-supercells, tracking across southern Illinois and into Indiana, leading to a wave of tornado warnings.

Nearly one out of every three tornado warnings issued were confirmed. These confirmed tornado warnings sometimes produced a debris ball visible on radar before dissipating minutes later. Despite these occurrences, substantial damage reports have not been noted, which is attributed to the short-lived nature of the tornadoes. Currently, 144 tornadoes have touched down in Illinois.

By Monday, the low-pressure system was expected to track eastward, spreading heavy rain into the Midwest and eventually the East Coast. More severe storms are anticipated to develop, which could produce large hail, damaging winds, and potentially more tornadoes. Rain, which could be heavy at times, is also expected in the Northeast through Monday, from Philadelphia to Boston.