Rising puffs cool by expansion, but continue upward as long as they are still warmer than the surrounding air. As long as the inversion remains intact, puffs of warm air cannot rise very far before encountering a layer of air of similar temperature and coming to a halt. As heating intensifies, some of the warmer puffs are able to push past the top layer and into the cooler air above. Once clear of the inversion, the puffs are able to rise much higher before encountering a layer of air of similar temperature. Small, wispy, clouds form when the rising parcels of air are finally cooled to their dew points.
Clouds formed by rising puffs lack flat bottoms and are short lived.
The small, poorly defined, clouds to the right of the peak in the picture above left are probably thermal puffs. Glider pilots watch for these clouds and consider their appearance an indication to get ready to launch as full scale convection is about to begin. As the sun rises higher in the sky, accelerating the rate of heating of the layer of air near the ground, thermal puffs become more numerous, larger, and often show obvious vortex ring, or partial ring shapes and the nocturnal inversion becomes increasingly unstable. At some point, usually well past mid morning, the nocturnal inversion abruptly collapses, a normal lapse rate condition is established, and large scale convective activity is triggered. Fully developed plume thermals appear.