A mesoscale convective system (MCS) that often forms in a zonal flow (upper level flow void of any major troughs or ridges).
Here's a better image that shows a number of features to include the overshooting tops and ripples (waves) in the very cold (and high) cirrus anvil.
Mesoscale convective systems (MCSs) or mesoscale convective complexes (MCCs) are a name given to a specific class of convection. Their characteristic signature is a rather large cold cloud shield that has a general round or oval shape as seen on the IR satellite image. Hard to miss. Not all MCSs are round...there's also a linear flavor as well.
The difference between the two isn't all that important, but it largely driven by the size and cloud top temperatures. A true MCC will have a general cloud shield with (1) continously low IR temperatures less than -32°C over an area >= 100,000 square km and (2) an interior cold cloud region with temperatures less than -52°C having an area >= 50,000 square km. So given that Iowa is about 150,000 square kilometers in size, I'd say that the first requirement was met...and the second requirement is pretty close to be an MCC versus an MCS. Also notice in the image above a very small area in southwest Iowa where the overshooting tops are white which references a temperature of -75°C or colder. Based on this sounding analysis below, this places the overshooting tops above 47,000 feet given that the tropopause is located at about 46,000 feet.
These monster systems are known for their ability to produce torrential rains, hail and high winds. They are noctural sytems that typically develop in the late afternoon/early evening and can persist throughout the night into the early morning hours. Some can even last as long as 24 hours or more. Most of the time the reflectivity image on NEXRAD is one that contains one or more significant bow-shaped echoes (hence the high winds).
They are not usually found in very virgorous atmospheric flow. In fact, the best conditions are associated with a weak synoptic-scale frontal zone and weak upper-level disturbances in the middle troposphere. So when you look at the upper level flow at 500 mb, for example, you don't see any major weather systems like we see during the fall, winter and spring. The height lines are basically showing a rather weak flow from west to east in the Midwest. This means they don't move very fast and can dump lots of rain. This is an important event from an agricultural perspective as long as it doesn't cause massive flooding or serious crop damage due to hail. These systems will often develop on the southern-most periphery of the height gradient.
