Virga over the Big Hole Mountains, Idaho

October 13, 2016

Virga 4 (1) October 2016 Viewer's Choice
: Glenn McCreery
Summary Authors: Glenn McCreery; Jim Foster

As shown above, glaciating virga was observed over the Big Hole Mountains of Idaho during the morning of October 1, 2016. Virga is rain that evaporates, or ice crystals that sublimate, before reaching the ground. On this early autumn morning ice crystals and not raindrops are falling through the warmer, drier air just below the cloud base. These clouds are likely composed of supercooled water droplets. Note that the Big Hole Mountains lie to the west of Teton Valley, Idaho, from where this photograph was taken. A few hours after this photo was taken, virga was no longer observed. By then, because the air was no longer so dry, ice crystals melted rather than sublimated and the resulting raindrops made their way toward the surface. Before noon rain was falling throughout the valley.

Photo Details: Camera Model: Canon EOS 5D Mark II; Lens: EF24-105mm f/4L IS USM; Image Date: 2016-10-01 8:00 a.m.; Focal Length: 105mm; Aperture: ƒ/8.0; Exposure Time: 0.0020 s (1/500); ISO equiv: 100; Software: Adobe Photoshop CS5 Macintosh.