Quick spiral flying south over Concord, NHAt Mckee Square in Concord facing east. First saw a single light moving at a distance. Assumed at first was aircraft over airport area. Object moved in a southernly direction. After noticing object was going too fast for a light aircraft at that distance, and too low for a larger aircraft, noticed a spiral formation coming behind it also moving south. Appeared to be a spiral moving upwards, heading south. Highly visible due to heavy cloud backdrop. Light seemed to be reflection of sunlight from partially clear sky in west.I am an open minded person, I can argue both for a weather phenomena, or for some type of operated craft. As I have never seen nor heard of a man made craft in this situation, nor observed such a weather based phenomena before, I decided to post.