Isolating clouds in video

[Jason Burnett]

I have a simple video created from hundreds of satellite images provided by NASA. It shows the static background of the earth with a focus on the East Coast of the United States.

I want to isolate the clouds by making the background transparent. In Photoshop, I would select a color range and sample the white color range masking and mask out the remaining pixels. 

I was hoping that After Effects had an equally simple solution that would filter every frame. 

What I am trying to do is generate an animated set of clouds based on NASA imagery that I can use as a layer in a 3D rendering of earth. If anyone has a better suggestion for how to accomplish this, I'm all ears.

Can anyone explain how to do this really simple task before I spend a week running actions in Photoshop on every frame?

[eikonoklastes]

Can you post a screenshot of the footage you're trying to work on?

[Jose Panadero]

You have some paths to do this. The first one is to use the Extract effect, located in the Keying category. This way you can isolate brighter or darker areas of your image. Another more advanced ways to do this is to use the Shift Channels effect combined with the Set Matte effect but you need to set what of the RGB channels of your images have enough contrast to create a matte.