With temperatures warming we're getting into that time of year when thunderstorms can form in the valley and Sierra. The amount of moisture we have to work with plays a huge role in whether we see rain, virga, or dry lightning. Virga is rain or snow that evaporates before it hits the ground. This forms a lot in our area because of the lack of moisture. Some say virga looks like jellyfish. There is a parent cloud with streamers coming down from it. Sometimes the rain has a hard time reaching the ground initially but eventually the air saturates enough to rain.
This is what happened over the weekend. The temperature and dewpoint were far apart around 6 p.m., but by 7 p.m. the air began to saturate. We got a trace of an inch of rain at the airport Saturday evening. Higher amounts in Sparks. When this happens at sunset it can make for some beautiful photos. We got some great photos last weekend on April 11th. The clouds formed a line with rain falling in some spots and evaporating before it hits the ground in others.
Virga can be a problem during a lightning storm. We need the rain to prevent fires. Virga can also cause gusty winds, making it dangerous to fly through. As the rain evaporates the air cools, and cool air sinks. This creates a rush of air spreading out in different directions. Virga can show up as false rain on radar.Â
