Forecasters Wednesday were closely monitoring a storm system over Iowa that was headed toward northern Illinois because it has the potential to cause significant damage — if it actually hits the Chicago area.

       There’s a whole lot riding on that two-letter word, said Todd Kluber, a meteorologist with the National Weather Service.

       “A lot of what we’re expecting in the forecast here is going to hinge heavily on how far south this initial batch of thunderstorms over Iowa can make it this far east. So, it’s kind of like a ‘Choose Your Own Adventure,’ where if this happens, then you go this route, and if that happens, you go that route,” he said.

       Kluber said the area “could get clipped” by the system that would likely move in around 6 p.m. If it did, that would be one of many factors that could help stave off more severe overnight storms, which would otherwise roll in between midnight and daybreak, said Brian Leatherwood, another meteorologist. If those storms materialize they’d likely be more severe, and area residents could expect hail and wind gusts as strong as 60 to 70 mph, which could down tree limbs or power lines.

       “Think of it like a score card,” Leatherwood said. “If we get hit this evening, that’s one point in this column, one factor out of several, where we’d be less likely to have these intense storms overnight.”

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       That’s because the first storm would stabilize the atmosphere, at least to an extent and for a few hours, making the second round of storms less likely. But in the other column, Leatherwood said, it will be cooler overnight and the effect from the first storm can only last so long or do so much.

       A woman relaxes on a hill in Palmisano Nature Park in Chicago July 13, 2021. (Terrence Antonio James/Chicago Tribune)

       “I do believe that showers and probably some isolated thunderstorms are increasingly likely (Wednesday evening) in the city,” Leatherwood said. “There’s still a lot of uncertainty with this.”

       Kluber said if the earlier storms stayed closer to the Wisconsin state line, in far northwest suburbs such as Harvard and Crystal Lake, a cold pool of air could form.

       “Which, when that occurs, would potentially produce multiple rounds of thunderstorms throughout the night and even potentially into a good portion of the day (Thursday),” he said.

       For more forecast information, visit the Tribune’s weather page.

       kdouglas@chicagotribune.com

       Twitter @312BreakingNews

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