Return of Polar Vortex to Trigger Midwest Storms, Chill

By , Expert Senior Meteorologist
July 12, 2014; 2:05 PM ET
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Rounds of thunderstorms, including severe weather, will affect the Midwest this weekend into Monday, ahead of a push of unseasonably cool air.

While the effect of the July sun and warm landscape will cancel some of the cool air, it will become surprisingly cool during what is typically the hottest time of the year.

According to AccuWeather Meteorologist Carl Erickson, "The pattern is reminiscent of a major polar plunge that occurred this past winter, which was referred to as the Polar Vortex."

A piece of the Polar Vortex, and a summertime version at that will break off from the Arctic and drop southward this coming week.

The pattern will not bring snow or sub-zero cold but it will bring angry clouds, cool air and the risk of waterspouts over the warmer portions of Great Lakes.

The pattern will deliver multiple days with high temperatures in the lower 70s in Chicago and Detroit and even a day or two with highs in the 60s in Minneapolis and other parts of the Upper Midwest.

For fans heading to the All-Star Game at Minneapolis, the it may seem more like football weather. Jackets and long sleeves may be needed by many fans to stay comfortable.

At night, temperatures could challenge record lows from the Midwest. Temperatures will drop into the 50s at night in many cities and will dip into the 40s in some of the suburbs and rural areas.

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The cooler air will move in aloft before reaching ground level. As this happens, an unstable atmosphere will trigger episodes of thunderstorms, some of which will be severe in parts of the region.

Sunday and Monday, the threat of severe weather will shift to the Northeast and southward through the Ohio and Tennessee valleys.

The greatest threats these days will be damaging wind gusts, flash flooding and frequent lightning strikes.

Cities in the threat zone on Sunday include Erie and Pittsburgh, Pennsylvania; Cleveland, Columbus and Cincinnati, Ohio; Indianapolis and St. Louis. The danger will shift to Charleston, West Virginia, Lexington, Kentucky, and Nashville, Tennessee on Monday.

Also on Monday, thunderstorms with small hail will erupt in the vicinity of Kansas City, Missouri.

After the cool air takes root in the Midwest through midweek, waterspouts will be a threat to boaters, fishing and beach interests over the southern portion of the Great Lakes.

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