In the united states, a mesoscale convective complex is most likely to develop in:

The answer is: The great plains

Mesoscale convective complex is an environment which characterized by constant heavy rainfall, wind and lightning. The organisms that live in this environment often nocturnal and have a long life span. In United States, Great plains such as  South Dakota, Wyoming , Montana, North Dakota,  Nebraska, Kansas all have this similar characteristics.

answer; code of federal regulations;