PORTLAND, Ore. (KOIN) — Rare noctilucent clouds were spotted over downtown Portland late Tuesday night.
The National Weather Service defines noctilucent clouds as “thin silvery-blue cirrus-like clouds frequently seen during summer twilight conditions at high latitudes (above 50°) in both hemispheres. These clouds are primarily composed of ice crystals at heights 50-70 miles above the Earth’s surface.”
Portland area sunsets remain within the early 9 p.m. hour as of Tuesday. These rare clouds were spotted nearly an hour and a half after sunset towards the northwestern horizon. These high, thin, ice-crystal-based clouds are still able to reflect sunlight well past the sunset hour…