Severe weather to threaten 18 states with storms, tornadoes

An 800,000-square-mile swath of the central United States will be at risk for rounds of severe thunderstorms, including the potential for tornadoes, starting late this week and continuing well into next week.

"Severe weather across the nation's midsection during the middle days of this week will be confined to localized clusters affecting only a fraction of the region," according to AccuWeather Senior Meteorologist Kristina Pydynowski.

A narrow band of thunderstorms is forecast to slice southeastward from Nebraska to Michigan and Indiana from Thursday afternoon to Thursday night. A few communities can be hit with severe weather and flash flooding. Chicago may be affected late in the day or during the evening.

"By Friday and into this weekend, multiple states will be at risk," Pydynowski said.

This several day outbreak will put at least 18 different states in the path of dangerous weather in the coming days.

There is a risk area highlighted for severe weather every day on the Storm Prediction Center (SPC) day four through eight outlook. This is the first time that has happened since that SPC product became operational in 2007, according to Harold Brooks, a senior scientist of the Forecast Research and Development Division at the National Severe Storms Laboratory.

AccuWeather estimates that about 44 million people live in the risk zone for severe thunderstorms from Friday to Sunday.

An active Pacific Ocean storm train will set the severe weather outbreak into motion. At the same time, warmth and moisture are forecast to build over the Plains and Mississippi Valley. A strong jet stream will stir the pot for severe weather soon after the storms cross the Rockies and come in contact with the warm and humid air.

The rounds of severe weather are coming at a time when travel and graduations begin to ramp up. Whether staying at home or on the road, be sure to stay up to date on the severe weather potential.

The tornado and high wind risk is likely to extend to after dark, which will add to the danger. It is possible that a few of the tornadoes may be large, violent and on the ground for more than a few minutes.

Large hailstones likely to be produced during the strongest storms can cause serious injury, kill livestock and cause substantial property damage.

Download the free AccuWeather app to help stay on top of severe weather watches and warnings. Keep checking back for updates on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.

Storms to erupt on High Plains Friday

"Heavy to locally severe storms may erupt near the northern boundary of warm air over northern Iowa and southern Minnesota during Friday," according to AccuWeather Meteorologist Jake Sojda.

The first widespread round of severe weather, which may evolve into a significant outbreak, is forecast to begin over the High Plains from eastern New Mexico and western Texas to southeastern Wyoming and southern South Dakota during Friday afternoon and evening.

The storms later Friday will erupt along the boundary separating dry air to the west and humid air to the east, otherwise known as a dry line.

These storms have the potential to bring very large hail and isolated tornadoes, as well as wind gusts to 80 mph and highly localized flash flooding.

Cities in the first wave of severe weather late Friday include Midland, Lubbock and Amarillo, Texas; Guymon, Oklahoma; Dodge City and Goodland, Kansas; North Platte, Nebraska; Lamar and Sterling, Colorado; Cheyenne, Wyoming; and Sioux Falls, South Dakota.

Clusters of heavy to severe storms are likely to continue, while progressing slowly to the east during Friday night over the Plains.

Severe weather threat to shift to lower Plains on Saturday

As a push of drier and cooler air shifts eastward Saturday, so will the threat of severe weather.

The threat for severe thunderstorms is forecast to extend from central and northeastern Texas to perhaps as far north as central Minnesota and southwestern Wisconsin during Saturday.

Damaging winds, flash flooding and isolated tornadoes are likely to be the main threats on Saturday.

The threat during Saturday afternoon and evening includes a number of major cities, such as Dallas; Oklahoma City; Wichita and Topeka, Kansas; Kansas City, Missouri; Omaha, Nebraska; and Sioux City and Des Moines, Iowa.

Storms to reach Mississippi River, perhaps Gulf coast on Sunday

On Sunday, the main threat of severe weather, including isolated tornadoes, will focus over the middle part of the Mississippi Valley.

Severe storms are likely to extend from southern Arkansas and northwestern Mississippi to southeastern Iowa, central Illinois and western Indiana.

However, there is a chance that severe weather will extend as far north as the central part of Wisconsin and as far south as southern Louisiana and part of the Texas coast.

New round of severe weather to begin on Monday

As another storm emerges from the Rockies, a new round of severe weather is likely to be sparked over the central and southern High Plains during late Monday and Monday night.

During Tuesday, the severe thunderstorm risk should once again advance eastward across the central and southern Plains and may reach from central Texas to northern Iowa and eastern Nebraska.

Similar to the round of severe weather into this weekend, the next round has the potential to produce tornadoes. However, the exact timing, nature and coverage of the storms may not be known until later this weekend.

As is often the case during late May, and especially during the amplified weather pattern, more rounds of severe weather are expected to follow beyond early next week.

The repeating rounds of thunderstorms and the heavy rain they contain are likely to elevate the risk of urban and small stream flooding, as well as send a new surge of water into area rivers and major waterways.