7 Altocumulus Clouds Mid-level clouds Cover sky Globular masses and rollsAssociated with rain or thunderstorms
8 Altostratus Sheets of blue and gray that cover most of the sky Sometimes thick enough to block the sun, leaving a light area in the skyAppear a few hours ahead of a warm front, and indicate a decrease in pressure.
9 Cumulonimbus Clouds Range in altitude Tall. Top in cold upper air with warm base. (anvil shaped)Called “thunderheads”From the warm base lightning, thunder and precipitation originate
10 CIRRUS CLOUDS High altitude clouds Ice crystals Thin, wispy, feathery Distant storm or change in weather
11 Cirrocumulus Clouds Very high altitudes Formed by ice crystals “mackerel sky”- small, globular, white masses or ripplesApproaching warm front or storm
12 Cirrostratus cloudsa layer of cirrus clouds that spreads across the skymake the sky pale or white in appearanceindicate approaching precipitation