al·to·stra·tus  (āl'tō-strā'təs, -strāt'əs)  n. An extended cloud formation of bluish or gray sheets or layers. [Latin altus, high; see al-2 in Indo-European roots + stratus.] |
| altostratus (āl'tō-strāt'əs) Pronunciation Key
Plural altostrati (āl'tō-strāt'ī') A mid-altitude cloud that extends in flat, smooth sheets or layers of varying thickness. Altostratus clouds generally form between 2,000 and 6,100 m (6,560 and 20,000 ft) and often produce long, steady rain showers. See illustration at cloud. |