These clouds are stratiform when the cold mass is stable and stratocumulus when the cold air is unstable. When the overrunning air is moist and unstable, cumulus and cumulonimbus clouds are frequently imbedded in the nimbostratus and altostratus clouds. In such cases, thunderstorms occur along with continuous precipitation. When the overrunning warm air is dry, it must ascend to relatively high altitudes before conden-sation can occur. In these cases only high and middle clouds are observed.
Visibility is usually good under the cirrus and altostratus clouds.
It decreases rapidly in the precipitation area. When the cold air is stable and extensive, fog areas may develop ahead of the front, and visibility is extremely reduced in this area. Integrated Publishing's Official Web Page Click here for a current index of everything on this web site. All Rights Reserved.