Clouds of the Day: Monday, December 20, 2021

Altocumulus: Today dawned with cirrus spreading overhead from the west. During the day, the cirrus was joined by a lower layer of altostratus. The first photo below shows wisps of cirrus mixed with thicker altostratus in the lower half and a sheet of darker altostratus in the upper half. The second photo shows thick altocumulus.

Altostratus

Altocumulus (cloud bases higher than 6,000 feet)

Surface temperatures warmed from the 20s into the mid-30s during the afternoon. Winds at the cloud level were blowing at 40 to 50 mph. By early afternoon the cirrus thickened with cloud bases dropping. By the time second photo was taken vertical tufts of altocumulus were visible. The clouds were still high, near the top of the level where middle clouds form and just below the cirrus level. The clouds in the second photo below are altocumulus. Look closely and you will see puffy clouds building out of the flat cloud bases - the telltale sign of cumulus.