AIR MASS THUNDERSTORM

An Air-mass thunderstorm, also called a garden variety thunderstorm, is a thunderstorm that is generally weak and usually not severe. These storms form in environments with low Convective Available Potential Energy (CAPE) values, low wind shear, and low helicity values. The lifting source, which is a crucial factor in thunderstorm development, is usually the result of uneven heating of the surface when it comes to air-mass thunderstorms. This is opposed to a lifting source being a cold front, a strong upper level jet streak, or a strong low level convergence boundary which is usually the case with other types of stronger storms. The energy needed for these storms to form comes in the form of insolation, or solar radiation. Air-mass thunderstorms do not move quickly, last no longer than an hour, and have the four threats of lightning, heavy rainfall, a weak downburst, and small hail (There could be 3/4 inch diameter (severe) hail in very rare cases). They are common in a maritime tropical air mass, around the gulf coast states, during the summer, and in the afternoon.
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Generally, a thunderstorm not associated with a front or other type of synoptic-scale forcing mechanism. Air mass thunderstorms typically are associated with warm, humid air in the summer months; they develop during the afternoon in response to insolation , and dissipate rather quickly after sunset. They generally are less likely to be severe than other types of thunderstorms, but they still are capable of producing downbursts , brief heavy rain, and (in extreme cases) hail over 3/4 inch in diameter. See popcorn convection .
Since all thunderstorms are associated with some type of forcing mechanism, synoptic-scale or otherwise, the existence of true air-mass thunderstorms is debatable. Therefore the term is somewhat controversial and should be used with discretion.