Severe weather threatens to pummel Midwest, Plains

(CNN) -- Baseball-sized hail, wind gusts and tornadoes are threatening to pummel parts of the central Plains and Midwest on Sunday and Monday.

A mix of ingredients could combine to spawn a severe weather outbreak sweeping through parts of Kansas, Oklahoma, Iowa and Missouri, CNN meteorologist Melissa Le Fevre said.

"Overall, the threat is similar for the region: strong supercells that will have the capability to produce hail baseball-size or larger, strong wind gusts and tornadoes," she said Sunday. "It will ultimately depends on how warm the region gets today."

According to the National Weather Service, supercells are a special type of thunderstorm that can last for many hours. "They are responsible for nearly all of the significant tornadoes produced in the U.S. and for most of the hailstones larger than golf ball size," the weather service says. "Supercells are also known to produce extreme winds and flash flooding."

Warmer temperatures are an important factor, Le Fevre said.

"Warmer temperatures allow for the air in the atmosphere to mix, which causes it to be unstable," she said. "Sunny days are essentially more unstable, which allows thunderstorms to develop and become strong to severe."

Beyond the Midwest, other areas were already seeing severe weather on Sunday. In Atlanta, serious flooding was reported amid storms producing heavy rainfall.

Here's a look at Le Fevre's forecast for several states:


Sunday: With Kansas temperatures 5 to 10 degrees above average for this time of year, supercells could develop. The storms could bring destructive hail and possible tornadoes for the afternoon, transitioning to damaging winds and heavy rain through the evening. Baseball-sized hail cannot be ruled out.

Monday: The surface front may stall on Monday, leading to showers and thunderstorms through the day. Localized heavy rainfall may lead to the need for flood watches and warnings.


Sunday: Storms are expected to develop after 2 p.m. (3 p.m. ET). Again, the threat of discrete supercells capable of producing large hail and tornadoes is present.

Monday: There is a similar threat for strong storms in the late afternoon. With the heavy rain that will occur through the weekend, flooding could become a problem Monday night.


Sunday: The greatest potential for severe weather will be in the late afternoon and into the early evening. Large hail could be the greatest threat. According to the National Weather Service office in Des Moines, the southern and western parts of the state could see the greatest chance for tornadoes. Overall, the main threat appears to be hail and wind. Rain is expected to decrease overnight.

Monday: Showers and storms are once again expected to develop on Monday afternoon. Large hail is possible and though the tornado threat looks low, it cannot be ruled out.


Sunday: Strong supercells and squall lines are forecast to develop in the late afternoon and continue into the early evening. The discrete cells will develop first before transitioning into squall lines or lines of storms. As before, the threats include very large hail and damaging winds along with the potential for tornadoes. Some of these could be strong. In St. Louis, the potential for severe thunderstorms will be present through the afternoon on Sunday. Large hail is expected to be the primary threat. Heading into the evening hours, damaging wind should pose the greatest threat.

Monday: Flooding is expected to become an issue after localized heavy rainfall. The weather pattern will not change drastically from Sunday to Monday, which is why we are still seeing a potential for severe weather for the start to the week. Again, afternoon storms could produce large hail, damaging wind gusts and possible tornadoes. In St. Louis, storms will reorganize during the afternoon and evening hours. Threats include large hail, damaging winds and the possibility of tornadoes.