by Caleb, KE0FOE
Virga is precipitation that falls through very dry air and evaporates or sublimates before it reaches the ground. It usually appears as dark, wispy streaks or shafts that extend downward from the bottoms of clouds.
Virga is usually observed over deserts and in other arid parts of the world, but it can happen almost anywhere there is enough dry air underneath clouds.
Virga is usually a harmless and benign phenomenon. However, in some rare instances, virga can potentially cause dangerous microbursts or even heat bursts.
More information about Virga can be found on Wikipedia: https://en.wikipedia.org/wiki/Virga, and some beautiful photos of virga can be found on EarthSky: http://earthsky.org/earth/virga-is-rain-that-doesnt-reach-the-ground