Why do thunderstorms sometimes not form on a very hot humid day?

Question

We got thunderstorms today in Virginia finally and its been an awesome sight with the lighting show but yesterday was hotter and just a humid but it was sky clear the whole entire day until sunset.

Why did thunderstorms blossom today as compared to yesterday? No front has moved in yet so that couldn't have been the reason. Maybe a capping inversion layer? If so what causes it to be higher vs. lower? What influences the capping inversion to prevent cloud development?

Answer 1

The most likely event was a strengthening of a mid-atmospheric capping inversion, which if sufficiently strong enough would stop rising air parcels that encounter the cap, thus preventing storm or even cloud formation.  The cap can be strengthened due to sinking air that occurs from a mid level ridge of high pressure.  The ridge can also be responsible for heat waves as it prevents air from mixing through a deeper later of the atmosphere, allowing it to heat more than it would otherwise.

Answer 2

Yup. A warm air cap. Very well said.. =)