By Korrina Grom
Update, 12:48 p.m.: The National Weather Service's Storm Prediction Center has now placed most of northern Illinois, including the Chicago area, in the "high risk" category for severe storms.
The severe weather is expected to develop across eastern Iowa, southwest Wisconsin and northwest Illinois this afternoon, according to the latest Hazardous Weather Outlook from the National Weather Service in Chicago.
"The storms will move east through this evening across all of northern Illinois and into northwest Indiana," weather officials said in the Hazardous Weather Outlook. "The timing for the strongest thunderstorms with the greatest probability to impact the Chicagoland area will likely occur between 6 and 11 p.m."
The primary threat, National Weather Service officials said, will be damaging winds.
"But they will be capable of producing tornadoes and large hail as well," weather officials added.
Update, 9:21 a.m.: The National Weather Service's Storm Prediction Center has now placed most of northern Illinois under a "moderate risk" category for severe weather.
"A moderate risk indicates a potential for a greater concentration of severe thunderstorms than a slight risk, and in most situations, the storms associated with severe weather are more intense," according to the Storm Prediction Center.
The latest Hazardous Weather Outlook, issued at 4:08 a.m., shows that thunderstorms could produce strong tornadoes, damaging winds in excess of 75 miles per hour, hail to the size of baseballs and very heavy rainfall.
"The combination of strong instability and strengthening wind shear will be favorable for a significant severe weather outbreak from mid-afternoon through this evening," according to the National Weather Service's Hazardous Weather Outlook.
In his forecast summary, Accuweather.com Meteorologist Anthony Sagliani said there is the possibility that a derecho—"a widespread, long-lived wind storm"—could develop.
"These showers and thunderstorms produce wind damage over a large swath of land," said Sagliani.
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Original story, 10:51 p.m. Tuesday: The entire Chicagoland area could see severe storms Wednesday afternoon and evening.
The National Weather Service's Storm Prediction Center has placed most of Illinois—including Lake County—in the "slight risk" category for severe weather on Wednesday, with a portion of Illinois south of Chicago in the "moderate risk" category. The Storm Prediction Center says a "slight risk" means that "well-organized severe thunderstorms are expected, but in small numbers and/or low coverage."
According to the National Weather Service office in Chicago, widespread severe weather will be a possibility on Wednesday.
"Some of the thunderstorms will have the potential to produce damaging winds, large hail and tornadoes," according to the National Weather Service's Hazardous Weather Outlook. "Heavy rainfall will be possible with any thunderstorm, which could lead to localized flash flooding."
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