CHICAGO — The Chicago area was placed under a conditional threat for severe weather overnight into Tuesday morning.

ABC7 Chicago meteorologist Larry Mowry said the most of the area is under a Level 1 threat. Some northwest suburbs were under a Level 2.

As for timing, Mowry said if any thunderstorms make it to the Chicago area, it would be between midnight and 4 a.m.

The upper Midwest braced Monday for severe thunderstorms with the potential for strong tornadoes.

The National Weather Service said the highest risks – a 4 on a scale of 1 to 5 – were in portions of southern Minnesota, including the Minneapolis area, northern Iowa and western Wisconsin. While forecasters expected two rounds of severe weather, the second, in the afternoon and evening, could be the most impactful.

“The most dangerous period is likely during the late afternoon and evening when strong tornado potential should be maximized. Scattered large to very large hail and damaging winds are likely as well,” meteorologists at the Storm Prediction Center in Norman, Oklahoma, wrote.

Depending on how the storms form, tornadoes in the EF-2 range or greater are possible, the weather service office for the Minneapolis area said.

The Storm Prediction Center said a lesser potential for severe weather extended as far south as parts of Texas and Oklahoma.

The City of Minneapolis on Monday reiterated its messaging to residents asking them to prepare. The city urged them to ensure they have multiple ways of getting weather alerts, are prepared to take shelter, secure outdoor furniture, and prepare for potential power outages by charging phones and other devices and having flashlights.

Monday’s first round of storms darkened skies over downtown Minneapolis around 9 a.m. and brought brief heavy rains, but it triggered no weather warnings as it passed through. The weather service said the situation for the afternoon’s main event remained volatile and could still spin up strong tornadoes.

The City of Minneapolis closed its public-facing non-emergency city facilities, including its main service center, as of 2 p.m. and activated its emergency operations center.

Some Minnesota schools canceled evening activities ahead of the storms, including the St. Paul and Bloomington School districts. Some Iowa schools also closed early for the day or canceled evening activities.

On Sunday evening, a tornado derailed an empty BNSF coal train west of Ashby in northwestern Nebraska. Initial reports were that a tornado measuring more than 1 mile (1.6 kilometers) wide derailed many of the approximately 130 cars on the train, toppling several onto their sides. There were no immediate reports of injuries and the locomotive remained upright, the News Channel Nebraska radio group reported. It was one of several tornadoes reported in that part of Nebraska on Sunday evening.

ABC7 Chicago contributed to this report.

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