Stratus

A low, flat, uniform cloud layer that forms in stable air, often covering the sky like a gray blanket. Stratus clouds typically produce drizzle or light rain and are associated with poor visibility, low ceilings, and IFR conditions. They commonly form when warm, moist air is cooled from below, such as by advection over a cold surface, or when a warm front overrides cooler surface air. Pilots should expect reduced visibility and ceilings below 2,000 feet AGL when stratus is present.