Watch: Lenticular clouds dance over Mt. Rainier as moon rises behind

Full moon rises over Mt. Rainier as a lenticular cloud sits parked on its summit. (Photo: Meg McDonald / Wild Northwest Beauty Photography)

VASHON, Wash. -- You should have known it was going to rain this week, and you didn't even have to check your phone's app or ask Steve Pool.

Mt. Rainier told you so -- it put up its umbrella on Tuesday.

Meg McDonald with Wild Northwest Beauty Photography shot an hours-long time lapse that provides a great illustration how lenticular clouds form and flow:

The cloud, also informally known as a "cap cloud" or "hat cloud", is formed when you have three ingredients: Warm, moist air that is just on the cusp of saturation, laminar flow (when you have winds constant with height -- as in little to no turbulence or shear) and something big to get in the way, like, say, the region's tallest mountain.

When the air flows over the mountain, it will create waves downstream where the air is now going up and down, and up, and down -- like ripples on a pond or waves on the ocean.

When the air goes up, it cools a little bit and when conditions are on the cusp of saturation, that slight cooling is enough to create a cloud. When the air sinks back down again, an opposite drying effect occurs and the cloud disappears.

While to us it might look like the clouds are floating in place, in fact, the air is streaming through the cloud as it hovers there -- the cloud is just showcasing the right spot in the atmosphere where the air is undergoing its lift and sink. Sometimes this occurs right over the summit, giving the mountain a hat.

Oh, and on this particular evening, the full moon provided a nice photobomb.

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