Middle Clouds - Altostratus (As)

Cloud-base heights for middle clouds:

Tropical Region Middle Latitudes Polar Regions
2-8 km 2-7 km 2-4 km
  • Altostratus Clouds - grayish/blue-gray
  • thin layer covering entire sky uniformly
  • found ahead of storms
  • can seen the sun through altostratus, but NO halo will be observed