The National Weather Service issued a tornado watch for all of northern Illinois until 9 p.m. Monday.
Forecasters advised that a few tornadoes were possible across the state and additional hazards, including ping pong ball-sized hail and wind gusts of up to 70 mph, were possible.
As of 3:15 p.m. Monday, a swath of rain and a few thunderstorms were traveling across northern Illinois. Additional storm development in west-central Illinois was expected travel into northern Illinois Monday evening with a greater potential for severe weather, said meteorologist Brian Leatherwood with the National Weather Service in Chicago.
No warnings for tornadoes or severe storms had been issued in northern Illinois as of 3:15 p.m., however.
The storms are a part of a low pressure system moving up from the southwest toward Illinois, Leatherwood said.
“It’s pumping up a lot of moist air in front it. We already seeing some pretty gusty winds. With that strong flow from the south, our atmosphere is going to be a little bit unusually moist for this time of year,” Leatherwood said.
Much of Illinois is under a “slight risk” for severe thunderstorms Monday, according to the storm prediction center.
Monday’s severe weather will likely come in two waves across northeastern Illinois, Leatherwood said. After the first wave moves through in the early afternoon, a second wave that could bring the potential for stronger storms, including tornadoes, will pass through after 5 p.m.
“If we’re going to see [tornadoes], it’s going to be more toward the afternoon time period,” he said.
Areas to the west toward Interstate 39 will not see as much of break between waves of storms that have already begun moving in, Leatherwood said.
All forms of severe weather are possible with the storms, Leatherwood said. He noted the same storm system produced tornadoes across Oklahoma on Sunday evening and has the potential to produce more in Illinois Monday.