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FARGO — If you have ever seen wispy or pointy, vaguely cloud-like things hanging underneath a cloud, what you may have been seeing is virga. Rain or snow that falls from a cloud, but dries up before making it to the surface, is called virga. If the air underneath a cloud is dry enough, precipitation falling out of the cloud can evaporate, sometimes making ragged wisps of cloud material.
Virga is especially common in atmospheres that are very dry, such as deserts. However, this occurs frequently in our region too, when a dry layer of air is between the cloud and the ground, causing the rain to evaporate before reaching the surface. When the precipitation persists long enough, the dry air may eventually saturate, allowing the precipitation to eventually reach the ground. Showers falling through dry air often are accompanied by a notable drop in temperature. It is the evaporation process which is responsible for this cooling.
