Severe storms to target Chicago, St. Louis and Minneapolis

As millions in the Midwest may cherish a return of hot and humid air during the last month of meteorological summer, AccuWeather meteorologists warn that one of the consequences of the pattern is likely to be rounds of severe weather through late this week and into early next week.

Steamy air is forecast to gradually build over the region in the coming days. However, unlike the setup for previous heat waves this summer, a massive heat dome is not expected to develop. Rather than a large northward bulge in the jet stream, the high-speed river of air sitting tens of thousands of feet up in the atmosphere will hover near the United States-Canada border. Weak systems, or ripples in the atmosphere, will ride along that path. Each of those ripples could trigger showers, thunderstorms and even locally severe weather.

Into Friday night, heavy, gusty and locally severe thunderstorms are anticipated to shift from southern Wisconsin and northern Illinois to part of northwestern Indiana, including a portion of southern Lake Michigan, AccuWeather Senior Meteorologist Courtney Travis said.

"Cities at risk for storms with damaging wind gusts, hail and flash flooding include Chicago, Peoria and Rockford, Illinois; Milwaukee and Madison, Wisconsin; and Gary, Indiana," Travis stated.

The storms are likely to remain strong to severe well into the Friday evening hours as they progress into part of the Lower Peninsula of Michigan, northeastern Indiana and part of northwestern Ohio. South Bend and Fort Wayne, Indiana; Detroit and Lansing, Michigan; and Toledo, Ohio, could be affected by the storms well after dark Friday.

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People beginning their weekend or heading home from work or school during Friday afternoon and evening in this heavily traveled zone could expect delays on the highways and at the airports.

The risk of thunderstorms and severe weather is not expected to end at the tail end of this week.

Even through the jet stream dip associated with storms into Friday night is forecast to weaken while moving farther to the east this weekend, showers and locally heavy, gusty thunderstorms cannot be ruled out in portions of northern Ohio, southern Ontario, northwestern Pennsylvania and northern and western New York state on Saturday. Meanwhile, a storm from the Southern states is forecast to climb the Atlantic coast this weekend with a zone of rain and thunderstorms for parts of the Interstate 95 corridor in the Northeast.

A larger dip in the jet stream, associated with a more vigorous system in the atmosphere, will drop southeastward across the North Central states this weekend, setting off the potential for a more widespread risk of severe thunderstorms.

The more widespread and significant severe weather threat could eye areas from central and northeastern Kansas to central Minnesota and part of western Wisconsin during Saturday afternoon and Saturday night, according to Travis.

Cities at risk for severe thunderstorms during the first half of the weekend include Topeka, Kansas; Kansas City, Missouri; Omaha, Nebraska; Des Moines, Iowa; Sioux Falls, South Dakota; Minneapolis and Rochester, Minnesota; and Eau Claire, Wisconsin.

"Strong wind gusts and torrential downpours will be common with the storms over parts of the Plains and Upper Midwest Saturday and Saturday night with incidents of hail and flash flooding likely," Travis said.

An AccuWeather Local StormMax™ wind gust of 80 mph can occur in the strongest storms on Saturday. There is also the potential for isolated tornadoes in some of the first storms that erupt during Saturday afternoon.

On Sunday, the threat is forecast to shift farther to the east and extend from Missouri to Wisconsin and the Upper Peninsula of Michigan.

Once again, the main threat from storms on Sunday will be for damaging wind gusts and torrential downpours with some incidents of hail.

"Along with the typical risks of severe thunderstorms on Sunday will be the potential for isolated tornadoes, especially in parts of northern and western Illinois," AccuWeather Meteorologist Isaac Longley said.

The threat of severe weather may once again extend to the Chicago area late in the day or at night on Sunday.

"St. Louis is among the list of cities at risk for severe thunderstorms during Sunday afternoon and evening as the city experiences the start of its fifth heat wave of the summer," AccuWeather Senior Meteorologist Dean DeVore said.

Highs are forecast to reach the mid-90s in St. Louis for multiple days starting on Sunday, while most of the North Central states can expect highs ranging from the middle 80s to the lower 90s from this weekend through much of next week, as a more typical mid-August weather pattern replaces the unseasonably cool conditions with low humidity that unfolded at the end of July.

During Monday, thunderstorms and perhaps the risk of severe thunderstorms are projected to advance eastward across the Great Lakes and the Ohio Valley.

Even though the storms will carry some threat to lives and property in the North Central states into next week, any non-flooding rain they bring can be of benefit to crops in the region. This is the critical time of year for moisture when corn, soybeans and other staples are filling out and reaching maturity.

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