Overview
- Storms are intensifying from the Plains into the Midwest with the primary severe window from late afternoon through the overnight, as SPC tiers place parts of the region under elevated risk levels.
- In the Chicago area, the National Weather Service highlights the greatest tornado potential near and south of I-80, with hazards including golf ball–size hail and wind gusts up to about 70 mph during the evening and night.
- Heavy rain is expected to train over some corridors, and NWS guidance flags a flood watch along and south of I-90 with widespread urban and flash flooding described as likely in parts of the metro.
- A second organized round arrives Wednesday as a strong cold front pushes east, bringing additional showers and thunderstorms from the Mississippi and Ohio valleys into western Pennsylvania, with some areas near Pittsburgh forecast to collect up to an inch of rain.
- Record or near-record warmth precedes the front, then temperatures tumble rapidly behind it, with many locations dropping from 70s on Wednesday to 40s or 30s by Thursday as the severe threat diminishes; officials urge multiple overnight alert methods for nocturnal tornado hazards.