What is a small scale current of air with vertical motion?

A small-scale current of air with vertical motion is an updraft. It is a localized stream of air moving upward, usually because warmer, less-dense air rises through cooler, denser surroundings.

Updrafts are especially important inside clouds. As moist air rises, it expands and cools; water vapor can then condense into cloud droplets or ice crystals. Strong updrafts help thunderstorms grow by lifting warm, humid air high into the atmosphere and suspending raindrops, hail, and snow.

Updrafts are not the same as broad atmospheric winds, which usually move horizontally over much larger distances. Their downward-moving counterparts are called downdrafts. Pilots and glider enthusiasts also watch for updrafts because rising air can provide lift, allowing birds, gliders, and some aircraft to gain altitude without continuously powered ascent.

A related term is convection: convection describes the larger process of heat-driven fluid movement, while an updraft is the specific upward current within that process.