Yosemite National Park: Get ready for a moonbow -- maybe

Ladies and gentlemen, don your raincoats. Conditions may be just right in the coming days for a moonbow at Yosemite National Park.

A moonbow, also called a lunar rainbow, occurs, oddly enough, at night. The Yosemite National Park website says an optimal view is the result of “clear skies, enough water in Yosemite Fall to create sufficient mist, dark skies, bright moonlight not blocked by the surrounding mountains, and the correct rainbow geometry.”

I can make no iron-clad promises, but Yosemite spokesman Scott Gediman said conditions look right: There is a lot of runoff at Yosemite Fall, the snow pack is enormous and the weather is warm.

Los Angeles Times photographer Mark Boster, whose Yosemite in Four Seasons photographic series has appeared in the Travel print section and whose photo appears above, recommends wearing a raincoat or poncho.

“Standing next to a roaring waterfall means bringing towels and plastic bags for your cameras,” he said.

He shot this photo using a 16mm-35mm zoom lens. The aperture was set at f/4.5, and he exposed it for 60 seconds.

Texas State University in San Marcos predicts a “very bright moonbow” from 9:30 to 11:50 p.m. Sunday at Lower Yosemite Fall. It also says to expect a moonbow at Upper Yosemite Fall the night/morning of Monday-Tuesday (11:05 p.m. to 12:05 a.m.) and from 1-1:40 a.m.Wednesday. (Other times are listed on the website.)

Of course, said Don Olson, of the department of physics at TSU, these predictions were made a while ago.

“When we did the moonbow calculations for 2011, over a year ago I think, we knew where the moon would be in the sky, but we had no way of knowing the depth of the Sierra snowpack in 2011 and the temperature,” he said in a recent email to me.

So even though it’s not a sure thing, this could be your big moment. Given the snowpack -- about 200% -- it could be a great year.