It's not very bright because so little charge flows from the cloud. The stream moves downward out of the cloud in fits and starts, traveling about 150 feet before stopping, and quickly starting again. Since the atmosphere is a good insulator, this weak charge snakes its way downward, often branching, trying to find the path of least resistance toward oppositely-charged particles. When each branch of a stepped leader forking from the cloud meets a rising streamer, multiple return strokes are generated. Each return stroke travels from the ground to the cloud in less than a half second, so all the channels appear to light up at the s ame time as forked lightning .
Stroke appears within a cloud or is obscured by nearby clouds.
Flashes of lightning can illuminate entire clouds, making them visible from miles away. With sheet lightning, the observer is near enough to hear the thunder. Flashes too far away for observer to hear the thunder. Like sheet lightning, these flashes are created by lightning bolts, but are in thunderstorms more than 10 miles away. Trees, buildings and urban noise can cut this distance to less than five miles.