"a sudden show of ‘mares’-tails’ high in the sky"
Cirrus Clouds (Mares' Tails)
GNU Free Documentation LicenseCirrus Clouds (Mares' Tails) - Credit: Rosarinagazo/Wikimedia Commons

Mares’ tails is a name sometimes given to Cirrus clouds, which are thin and wispy and often accompanied by tufts. A high number of these clouds may indicate stormy weather to come, or be the remnants of a thunderstorm.