How can I mask this transition with a noise texture?

Hello! I have this shader that uses World Aligned Blend to have the snow function on the z-axis. The problem is that I need a more realistic transition than this.
I have tried to mix with a multiply node the aplha of world aligned blend and the noise texture, Also mix the functions with a height lerp function…
but it has not worked…
How can I mask this transition with a noise texture? Thank you! :slight_smile: