What does "Virga SW" refer to in aviation meteorology?

In aviation meteorology, the term "Virga SW" specifically refers to rain that evaporates before it reaches the ground, indicated by the 'SW' which designates the direction of the rain's origin—southwest. This phenomenon occurs when precipitation falls from a cloud but encounters a layer of drier air below, causing the droplets to evaporate before they can make contact with the surface.

Understanding virga is crucial for pilots and air traffic controllers because it can impact visibility and weather conditions in the vicinity of an airport. That's why knowing that virga indicates evaporating rain helps in anticipating potential weather-related challenges during flight operations. The other choices do not accurately describe virga; for example, rain falling towards the ground would imply it's reaching the surface, which contradicts the definition of virga, and a type of cloud formation or strong wind direction do not pertain to the specific phenomenon of evaporating rain.