Ali
For creating that Glow in the the Sky, Make a Yellow (or any other color)solid and make an Elliptical Mask on it. Now feather it to 300 to 400 % so that there is no hard edge.
Put this solid layer above your cloud layers and then then apply GLOW Effect to it.
For making clouds there are many ways. You can create realistic clouds in 3D application like Maya which has inbuilt presets for it.
Also Video copilot has Real Clouds Footage Collection which you can use:
https://www.videocopilot.net/products/realclouds/
You can create clouds like this using Trapcode Particular too.
Here is a tutorial for creating clouds using particular:
https://vimeo.com/22671370
Vishesh Arora
3D and Motion Graphics Artist
Films Rajendra
Blog:
https://digieffects.wordpress.com
Demo Reel(3D):
https://www.youtube.com/watch?v=lHPgIJU_BR8