Virga is precipitation that evaporates before it hits the surface of the earth.
Meteorologists refer to virga on radar when the precipitation is occurring in the upper levels of the atmosphere (and the radar beam detects this) but, the drops evaporate before hitting the ground.
A good example of this is the Empire State Building. Many times, it might be raining at the top of the Empire State Building, and nothing is happening at the ground.
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