What is ‘virga’?

Weather

The past few days, we’ve seen light rain on our Central Texas radars, but most rain gauges have remained dry.

This is due to a phenomenon called “virga,” or rain that fails to make it to the surface.

It happens when a dry airmass is in place at the surface of the earth for a variety of reasons, including winds ushering in dry air, low humidity and/or high heat.

As rain falls through this layer of the atmosphere, it evaporates before hitting the ground.

Graphic courtesy of The National Weather Service

Virga is typically harmless as it’s usually light rain falling that evaporates. But in some cases, heavy rain from thunderstorms can still fall as virga, and the downburst winds associated with the heavy rain can still make it to the surface causing damage to structures.

Virga can look very pretty as it falls and can be even more dramatic at sunrise or sunset.

Photo of a virga shower, courtesy of The National Weather Service

Virga is derived from Latin, which means “branch” or “twig”, possibly coming from how it looks as it’s falling from the sky.

Next time you see rain on radar over your house, but no rain is actually falling, the radar isn’t lying to you! There’s just more than likely dry air at the surface and it’s evaporating before it reaches your backyard.

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