Why do MCS/MCC's form at night?

[Peter B. Creedon]

Back in college, my meteorology professor taught us that MCS's and MCC's form during the overnight hours. Why is this?

 

[Jeff Duda]

That statement is not entirely true - plenty of MCSs and MCCs form during daylight hours. However, probably the leading explanation underlying that statement is the forcing from the nocturnal low-level jet. During the daytime, cellular storm modes are usually preferred given the more heterogeneous nature of forcing to trigger convection (although even that is not always true).

 

[Peter B. Creedon]

That statement is not entirely true - plenty of MCSs and MCCs form during daylight hours. However, probably the leading explanation underlying that statement is the forcing from the nocturnal low-level jet. During the daytime, cellular storm modes are usually preferred given the more heterogeneous nature of forcing to trigger convection (although even that is not always true).

I noticed that a lot of these constitute part of the STL areas "big" events. They come through the area during the morning hours, setting the stage for the main event in the afternoon/evening hours.