‘Strong to intense tornadoes, very large hail' possible in Midwest Monday

Editor's Note: The latest weather story for Monday, April 28 can be found here. Our original story continues below.

Parts of the upper Midwest are at significant risk of a severe weather outbreak Monday, with “strong-to-intense” tornadoes and massive hail among the threats.

According to the National Weather Service and the Storm Prediction Center, the greatest risk of severe weather can be found in a large area of the upper Midwest that encompasses southeastern Minnesota, including the Twin Cities, as well as western Wisconsin and northern Iowa.

The NWS says that a severe outbreak is "likely" across portions of the Midwest and the upper Midwest, with "strong-to-intense tornadoes" possible and "large-to-very large hail" also possible.

Even outside of that area, most of the Midwest is at an elevated risk of severe weather, with gusty winds, damaging hail and tornadoes all possible across an area populated by tens of millions of residents.

As of Sunday morning, the Storm Prediction Center estimates a roughly 10% chance of an EF2 or stronger tornado occurring within 25 miles of any given point in a wide swath of the upper Midwest on Monday, including most of Iowa, southeastern Minnesota, western Wisconsin and even parts of northwest Illinois.

An EF2 tornado packs wind gusts of up to 135 miles per hour according to the Enhanced Fujita Scale, with stronger tornadoes also possible according to forecast models.

The main area of concern is in Iowa southern Minnesota, an area that includes the Twin Cities, Des Moines and Cedar Rapids, according to forecast models.

Tornadoes could also occur outside of the area, with a chance of tornadoes in an area stretching all the way from the panhandle of Texas into western Michigan and the upper peninsula of the state.

The Chicago area is at the lower end of the risk categories, with roughly a 2-to-5% chance of a tornado forming within a 25-mile radius, but tornadoes cannot be ruled out, according to forecast models from the NBC 5 Storm Team.

According to the National Weather Service’s Omaha office, parts of Iowa and southern Minnesota could also see potentially devastating hail of up to three inches in diameter. Hail of that size would be larger than a baseball, and could cause significant damage to vehicles and homes, and could kill livestock and other animals caught outdoors.

A large swath of the Midwest is at a 30% risk of hail one inch in diameter or greater (roughly the size of a quarter), which can also cause damage to vehicles and homes. That risk area includes nearly all of Iowa, as well as eastern Nebraska, northern Missouri, northwestern Illinois, all of southern Minnesota and nearly all of Wisconsin, according to the SPC.

Other parts of the Midwest, including parts of northern Illinois, are at a 15% chance of such hail occurring, an area that includes Chicago and Milwaukee.

Finally, wind gusts of up to 75 miles per hour could potentially occur, downing tree branches and power lines and even damaging the exterior and roofs of homes.

Wisconsin is especially at risk of damaging winds, along with northern Iowa and far northwestern Illinois. Most of northern Illinois is at a slightly lower risk level, but residents are still urged to use caution and to be on the lookout for watches and warnings Monday.

According to the NBC 5 Storm Team, the threat of severe weather diminishes further to the east and southeast of the main center of the storm threat. That leaves most of the Chicago area at a “slight” risk of severe weather, the second of five threat levels used by the SPC. Northwest Indiana is at a “marginal” risk of severe weather, a step below that threat.

There is some indication that storms could break up before they reach the Chicago area, with the arrival time expected to be extremely late on Monday or even early Tuesday morning, according to forecast models.

Still, gusty winds are expected regardless, and any storms that do develop could at the very least accelerate those winds and caused downed branches and power lines. Heavy rain could also occur, along with frequent lightning.