37 What are the characteristics of stable air?
B. Poor visibility and steady precipitation.
From: FAA-H-8083-25B, "Pilot’s Handbook of Aeronautical Knowledge"
Chapter 12, "Weather Theory", Page 12-17, Air Masses
"An air mass passing over a colder surface does not form convective currents but instead creates a stable air mass with poor surface visibility. The poor surface visibility is due to the fact that smoke, dust, and other particles cannot rise out of the air mass and are instead trapped near the surface. A stable air mass can produce low stratus clouds and fog."
This is correct.