_______ is type of thin, feathery cloud known as 'mare's tails'. Happens in fair weather, and will rain or snow within several hours. _______ are white, founded, puffy clouds that happen in fair weather. _______ are tall, dark storm clouds happens in thunderstorms and tornadoes. _______ are gray, flat clouds that look like blanket covering the sky, letting in little sunlight - happens with light rain and drizzle.