Severe threat to ramp up across Midwest

After a long stretch of rather quiet weather for much of the Midwest, an approaching storm system will act to shatter the serenity for some residents on Sunday.

Following seemly endless rounds of severe weather during the summer, the general weather pattern across the Midwest for much of autumn has been largely unremarkable in terms of feisty weather. However, the same storm system that brought heavy rain and some mountain snow to the Northwest to end this past week, will change that trend as it continues to push eastward early this week.

A potent cold front associated with this storm system will be the main driver steering explosive storms on Sunday.

"Thunderstorms are expected to initiate across the eastern Dakotas by midafternoon Sunday, with the primary threat being damaging winds, and hail," AccuWeather Meteorologist Brandon Buckingham said. "As the afternoon progresses, the thunderstorms are expected to form into a single squall line."

This squall line will likely first develop in the late afternoon out ahead of a cold front stretched from from far eastern North Dakota, south into northeastern Nebraska. As the cold front marches eastward into the evening hours, the squall line will elongate and ultimately stretch from central Minnesota, through central Iowa and into southeastern Nebraska.

"Through the evening hours, damaging straight-line winds will likely become the primary threat from thunderstorm activity," Buckingham added.

An AccuWeather Local StormMax™ of 70 mph is forecast as damaging winds tear across portions of the north-central United States.

Travel disruptions are likely to develop across the region as these severe storms also unleash hail and torrential downpours through Sunday evening.


"Residents and travelers along the Interstate-29 corridor from Fargo, North Dakota, southward to Omaha, Nebraska, could all face rapidly changing conditions as thunderstorms explode and track over the area," Buckingham said. "Motorists traveling along interstates 30, 80, 90 and 94 will want to keep a close eye on the sky for approaching thunderstorms."

As the cold front pushes eastward overnight Sunday, thunderstorms and heavy downpours will continue to march eastward and reach Wisconsin, western Illinois and Missouri by sunrise Monday.

"The threat for severe weather is expected to diminish considerably in this time," Buckingham added.

As the cold front tracks into the Great Lakes on Monday, it will encounter a more stable air mass where not all of the ingredients needed for widespread severe weather will be in place.

Rather than a widespread threat for damaging wind gusts or hail, any storms that develop ahead of the front on Monday will mostly act as rainmakers.

Unlike Sunday's organized squall line, periods of heavy rain and a few locally gusty thunderstorms will develop across much of the Great Lakes on Monday. Impacted areas will include portions of the Canadian province of Ontario, south to northern Illinois and Indiana.

Generally, up to an inch of rain is expected to fall across the Great Lakes on Monday. However, a few locations caught under the heaviest downpours can easily record up to 2 inches of rainfall. Areas most likely to encounter the heaviest downpours include northeastern Minnesota, northern Wisconsin and northern Michigan, including the Upper Peninsula.

Flash flooding can develop as a result of heavy rain, especially in low-lying or poor-drainage areas.

While Monday's rainfall can lead to flash flooding issues for some, rain will be beneficial for others. Although many areas across the Great Lakes region recorded near-normal rainfall amounts in September, a few drier locations will greatly benefit from this rain event. A handful locations across Minnesota, Illinois, Michigan and Indiana are currently experiencing either abnormally dry or moderate drought conditions, according to the United States Drought Monitor.

Related: Midwest snowstorms

Once such location is Duluth, Minnesota. In September, Duluth recorded a total of 0.85 of an inch of rain--only 21% of its average rainfall for the entire month. The city has yet to record any precipitation this month, but Sunday night into Monday will likely end its dry streak with a quick 1-2 inches of rain possible.

The Great Lakes will not be the only region to deal with drenching rainfall on Monday. A combination of the remaining moisture from what once was Hurricane Delta and moisture from the Atlantic Ocean will work to unleash heavy rain on portions of the mid-Atlantic and the Northeast on Monday.

Quiet weather will return to much of the nation's midsection on Tuesday as a large area of high pressure is set to develop over the Ohio Valley. This area of high pressure will work to keep areas from the Midwest to the Southeast dry and pleasant into at least midweek.

Keep checking back on and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.

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