Change canvas size to 800 x 400.
Start by inserting a new layer. Name it "1".
Select the Brush tool, setting the thickness to 10, hardness 100%.
Set the grey to this dark grey.
Start by drawing lines for the mountains.
Fill with the Paint Bucket (click 2x so it fully fills)
Draw mountain silhouettes in 4 different layers.
Go to Adjustments > Hue/Saturation and bring up the Lightness slider for each mountain - lightest shade in the back, darkest at the front.
For each layer, smooth out the edges with Effects > Noise > Median
Mountain colors: First set to default (black & white), switch colors so white is Primary and then go to More... change "V" slider down to %s:
- Lightest - 80% white
- 60%
- 40%
- 20%
New layer for trees in the front - big Brush, black. Paint along bottom to fill in area. Then draw with smaller brush tree shapes - very rough. Then Crystalize
Also crystalize the front mountains.
Draw in new layer some white snow for the back mountains with a small brush. Shape with Eraser. Then Median to soften/smooth edges.
Select the Gradient Tool and choose 2 colors for your sky.
Drag it up/down on the Background layer.
Add clouds using Callout shapes in new layer, behind mountains.
Mountains - add Glow - reduce Radius a bit, Brightness all the way to the bottom.
Glow for clouds & trees - slide Contrast & Brightness all the way to the left.