Definition
A common name for cirrus clouds that appear as long, thin, wispy streaks of ice crystals high in the atmosphere, often curving or trailing across the sky. Their presence frequently indicates an approaching warm front or a change in weather within the next 24 to 36 hours.
Plain English
Wispy, feathery white clouds high in the sky that look like flowing strands of hair. Pilots watch for them because they often appear a day or so before weather changes.
Context Anchor
Pilots may notice mare's tail clouds during preflight weather checks, in weather reports, or while scanning the sky before or during a flight.
Derivation
Named for the resemblance to the long, flowing tail of a horse (a mare). Sailors and farmers used the term for centuries before aviation adopted it, because these clouds reliably signaled changing weather.
Why Pilots Care
Often signals an approaching warm front or changing weather that may affect flight conditions.
Grounding Statement
Picture long, fine streaks of white pulled across a blue sky like brushstrokes — that's a mare's tail.
Intuition Check
Do not read mare's tail as a low cloud or a surface feature. In aviation weather, it means a high, wispy cloud pattern that may point to changing weather aloft.
Example Sentence 1
During preflight, the pilot noticed mare's tails to the west and checked the forecast for an incoming front.
Example Sentence 2
Mare's tail formations appeared ahead of the cold front, prompting an earlier departure.