Fetching details from the dictionary...
to become clouded; to darken; to get dark; to become hidden (behind clouds)
to darken (of a face)
to worsen; to deteriorate; to become gloomy
ピクニック中に空が陰った。
The sky clouded over during the picnic.
悪い知らせに、母の顔が陰っていた。
Her mother's face had darkened at the bad news.
過去を思い出すたびに、彼の表情は陰るのだった。
His expression clouds over whenever he remembers the past.