Editing Cirrus cloud (section)

=== Cirrostratus ===
{{Main|Cirrostratus cloud}}
[[File:Close Cirrostratus.jpg|thumb|alt=Milky-white cirrostratus clouds cause the sky to appear lighter and have a milky tint.|Cirrostratus cloud]]

Cirrostratus clouds can appear as a milky sheen in the sky<ref name="common-clouds"/> or as a striated sheet.<ref name="H&H-340"/> They are sometimes similar to altostratus and are distinguishable from the latter because the Sun or Moon is always clearly visible through transparent cirrostratus, in contrast to altostratus which tends to be opaque or translucent.<ref name="Day-56">{{harvnb|Day|2005|p=56}}</ref> Cirrostratus come in two species, ''fibratus'' and ''nebulosus''.<ref name="common-clouds"/> The ice crystals in these clouds vary depending upon the height in the cloud. Towards the bottom, at temperatures of around {{convert|-35|to|-45|C|F}}, the crystals tend to be long, solid, hexagonal columns. Towards the top of the cloud, at temperatures of around {{convert|-47|to|-52|C|F}}, the predominant crystal types are thick, hexagonal plates and short, solid, hexagonal columns.<ref name="parungo-254"/><ref name="parungo-256">{{harvnb|Parungo|1995|p=256}}</ref> These clouds commonly produce halos, and sometimes the halo is the only indication that such clouds are present.<ref name="ahrens-120">{{harvnb|Ahrens|2006|p=120}}</ref> They are formed by warm, moist air being lifted slowly to a very high altitude.<ref>{{harvnb|Hamilton|2007|p=24}}</ref> When a warm front approaches, cirrostratus clouds become thicker and descend forming altostratus clouds,<ref name="cloud-classification"/> and rain usually begins 12 to 24 hours later.<ref name="ahrens-120"/>