Definition
A high-altitude cloud type composed of ice crystals, appearing as a thin, sheet-like or veil-like layer that often covers large portions of the sky. Cirrostratus clouds form above 20,000 feet and are transparent enough that the sun or moon remains visible through them, frequently producing a halo effect. Their presence often indicates approaching moisture and a possible warm front within 12 to 24 hours.
Plain English
A thin, wispy sheet of cloud high up in the sky, made of ice crystals. It looks like a pale veil — you can still see the sun or moon through it, often with a ring around it.
Context Anchor
Pilots encounter cirrostratus in weather training, preflight weather review, and visual checks of the sky before or during a flight.
Derivation
From Latin 'cirrus' meaning 'curl' or 'tuft of hair', and 'stratus' meaning 'spread out' or 'layered'. So cirrostratus is literally a 'spread-out wispy cloud' — high, thin, and layered across the sky.
Why Pilots Care
Often signals an approaching warm front that may bring lower ceilings or reduced visibility later.
Analogy
Cirrostratus can look like a thin white veil pulled across the sky. You can still see light through it, but the sky no longer looks clear and blue.
Grounding Statement
Picture the sun shining through a pale, milky sheet that covers much of the sky; that sheet-like high cloud is cirrostratus.
Intuition Check
Do not confuse cirrostratus with low, gray stratus cloud. The “cirro” part means this cloud is high, even though the “stratus” part means it is layered.
Example Sentence 1
A thin layer of cirrostratus spread across the sky, producing a faint halo around the sun.
Example Sentence 2
Cirrostratus appeared ahead of the flight path, prompting the pilot to review updated forecasts for possible weather changes.