The UCAR Center for... PDF Cloud Classifications and Characteristics at what elevation are mid level clouds.
The middle level clouds have bases between 2000 and 7000 m.
Altostratus clouds are middle level clouds composed of ice crystals and water droplets.The clouds cover the sky.The sun can be seen as a round disk in the thinner areas of the cloud.Altostratus clouds form ahead of storms that will produce precipitation.
Altocumulus clouds are middle level clouds that are made of water droplets and are sometimes rolled out in parallel waves or bands.The appearance of these clouds on a warm, humid summer morning can lead to storms later in the day.