This is a photograph of cirrostratus clouds near Moab, Utah.
Click on image for full size
Courtesy of Anne Pharamond
Cirrostratus (weather symbol - Cs) clouds consist almost entirely of ice crystals and belong to the
High Cloud (5000-13000m) group. They are sheetlike thin clouds that usually
cover the entire sky.
The sun or moon can shine through cirrostratus clouds . Sometimes, the sun or
moon will appear to have a halo around it when in the presence of cirrostratus.
The ice crystals from the cloud refracts the light from the sun or moon,
creating a halo. This halo is the width of your hand when you hold it out at arm's length.
Cirrostratus clouds usually come 12-24 hours before a rain or snow storm. This
is especially true if Middle group clouds are associated with it. You
can distinguish a cirrostratus from an altostratus cloud by looking for your
shadow on the ground. If you can see your shadow, then the cloud is
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